My first telescope

If you want to learn your way around the sky you need two things:

1. Dark skies

2. Decent aperture

The second one rules out a small refractor, the first one rules out a mid-sized dobsonian if you need to travel and you don't have your own means of transportation. A star tracker won't do for visual observing. 

So the answer to your queries is get the largest APO refractor you can afford which basically is going to be a 80mm aperture telescope and do AP or EEA only. And get a larger camera or a DSLR. And means to power it that you are confortable toting around as well the necessary computer hardware (if using an astro-camera, you can dispense with it using a DLSR).

Hi!
I find it a bit unclear from your post if your main goal is visual observations or astrophotography. 
Sadly, these have very different requirements, and if you try to go for a compromise you are likely to end up with equipment that does't do either of these things too well. 

Let me briefly elaborate on what I mean. I'm assuming deep space photography here, solar system imaging is yet another thing.
In astrophotography the most important things are stable tracking and well corrected optics. (in this order). 
You can get excellent results with a very small, but high quality telescope. It is actually often preferable over larger scopes because it's easier on the mount. 

In visual observations however, size matters. And actually size matters basically over everything else. You will see so much more with the simplest 8" Newton on dobsonian mount than the highest possible quality space-engineered apo refractor which is the size of your forearm. 

So this basically consitutes the answer to one of your last questions
- Should I get 2 telescopes, 1 small (AP) for astrophotography and 1 larger (AC) for onserving?
If you want to do both - yes. However you can simply focus on one thing for now and just accept that the astrophotography set you get won't let you do any observing (or the other way around). 

It also kinda answers your other question:
- What focus lenght do I need?
This is up to you, but keep in mind the golden rule. The most important thing in deep space photography is precise tracking. And "precise" is a relative term. The easiest way to understand it is that the precision of tracking should correspond to your scale. If a single pixel covers 6.74x6.74 arcsec of the sky  (that's the value for canon 6D dslr and 200mm focal length), then 3 arcsec tracking precision is absolutely good enough. 
If you go for a focal length of 800 mm and pair it with a small pixel camera like asi2600 you end up with 0.97"x0.97 scale and the 3 arcsec tracking precision doesn't sound too good any more. (this is just an example, not considering the budget here). 

- Can I use startracker in the same way as a normal EQ mount?
A startracker is literally a normal EQ mount. Means the same thing, the term is just usually used to describe the small eq mounts ;) 


Before I make a concrete recommendation let me just say one more thing. 
You're saying you don't want a goto mount. I appreciate your motivations, but let me tell you: you do want a goto mount if you seriously want to pursue astrophotography, you just don't know it yet. Nothing stops you from not using the goto functionality, but having it is an absolute game changer for many reasons.
1. finding stuff in space is damn hard. And while it's really fun to play around to find bright stars or objects such as M31 or M42, try doing that with a dark nebula which you won't even see after you've found it, because you need a multi minute exposure to confirm. Trust me, it's frustrating as hell in the long run even if it does seem fun initially. 
2. repetitive framing. If you end up actually doing astrophotography, you'll find sooner or later that sometimes a single night session is just not enough. Now imagine that you spend an hour looking for the object, and the next day you need to spend 2 hours for the same thing, because not only do you need to find it again, you need to find it with precision of a few pixels to have the same framing!
3. time. This relates to the stuff already mentioned. If you have an object visible you want to photograph and it will be visible for another 5 hours (2 of which very low over the horizon), you want to take 3 hours of exposure!

If you want to practice finding stuff, the forementioned newtonian telescope on a dobsonian mount is a great way to do it. Getting a non-goto mount for astrophotography is just not. 

Now with all that said, here is my recommendation for what to buy for the budget you have with brief explanations of the choices. Keep in mind this is just an example, there is no one right answer. 
1. Sky-Watcher EQM35 PRO for 809 euros. Did I just ignore your non-goto requirement and recommended a mount with double the lifting capacity you mentioned? yes. And I think I already explained myself above well enough. On top of that, it has an awesome feature that I don't think any other mount has. You can partially disaseemble it to convert it to a light weight sky tracker able to support a DSLR camera with a lens which answers your backpacking needs (which I think are utopian but that's off topic and I'm happy to discuss it later).
2. TS-Optics PhotoLine 60 mm + TsRed08-60 reducer-corrector for 680 euros. (f=288mm) This is just a doublet, but it's surprisingly potent and with the reducer it becomes pretty fast (f/4.8). It will also work reasonably well even with full frame sensor which brings me to:
3. Canon 6d mk1 astromod (used) for 340 euros. It is an extremely potent camera for the price. It has a reasonably big pixel (I already explained the benefits) and low noise sensor. I am currently selling one for that much, so I used that as the price. They usually go for a bit more, but you can also get one a bit cheaper if you're patient and observe the marketplace ;) 

we arrived at 1829 euros. I used currently available prices as estimates. The mount is from polish shop teleskopy.pl (which i highly recommend, their website is aweful but they are a good store with mostly unbeatable prices and they ship eu wide for fixed price). The scope is currently on sale in teleskop-express.de 
Let me keep going, stay with me

4. Asi 120 mm mini (used) for 120 euros. They usually go for a bit more, but again, I recently sold one for this exact price so I use that as an estimate
5. cheapest guiding scope you can find used (literally any will do) for 50 euros
6. asiair mini for 150 euros (currently available on astrobin marketplace for that much). 

This adds another 320 euros with a grand total of 2149 euros plus shipping costs, let's say 2200. Notice how I totally ignored the fact that you already own the ASI224MC camera? That's where you get the extra 200 euros (well, that's a bit optimistic, but you should get at least 150). 
While this is by no means a bad camera, it's not suitable for deep space photography whatsoever. It's a typical planetary camera. 
Alternatively, you can skip the asi120mm in the above set and use your ASI224MC for guiding. 


Let me just quickly summarize all this 8 hour post  
What I'm proposing is totally not what you asked for. But this is what I would get if I were you having the experience I have. It's a full and very potent astrophotography set. Additionaly, whenyou feel like investing more money (notice how I used "when" and not "if"?) you can easily exchange it piece by piece already owning a mount which will take much more. 
Just as an example: want a bigger telescope? No problem, sell this one, but a 80mm apo and everything will work. Want a quality of life improvement? Just add an autofocuser. Wanna do some visual observations? Take your mount and put a 150/750 newtonian on it, it will take it just fine! 


- What filters do I need?
initialy none. Leave that for the future ;) 



PS: whoa that was long and I feel like I have so much more to say xd

You're landing in the exact pitfall I warned you about in the first few sentences of my answer. 
Ed80 is too small for visual observations. Yes, you will see SOMETHING but really not much. 
It's also waaay too big for the mount you chose, especially for astrophotography. Notice it's focal length as well. There is absolutely no way youll get stable tracking. 
I would even argue it's too big for the eqm35, but you may get away with this using a big pixel camera. But the gti is simply not going to do

Here is what I'll probably buy now:

Telescope: Skywatcher Evostar ED80 -
Mount: Skywatcher Star Adventurer GTi - because it can have batteries and thats why not bigger EQ3.

OK. you need to slow down and not buy anything yet.

the Star adventurer is not big enough to swing an 80mm refractor with any level of success for AP.

star adventures are designed to carry DSLR and DSLR Lenses or very small telescopes.

many people shoot with DSLR lenses when they start out, myself included. I had a lot of fun with a DSLR way back when...

some of the iOptron mounts are very light and portable if moving around is your thing, and DSLRs are lightweight and portable too.