Should I give up? - I don’t event want to make money with it...

I don’t know if I picked the right „battle“. I see lots and lots of other (very well designed and well-funded) teams fail with their solutions in this space. So, I don’t know if people really „need“ such an app, if it is helpful at all or if this niche is too difficult to "crack" (e.g. this type of app requires a lot of discipline, steep learning curve etc.)

Possibly. The "productivity" domain is overcrowded with very little differentiation. Could you succeed? Possibly. With what you have? Hardly. This domain is possibly ripe for disruption but a difficult niche to crack, as you put it.

I still believe in the ideas behind Mission Control. However, I don’t know if I have the time and energy to continue to improve the app/remove bugs or convert this to a native app/work on instructions/guidance and promote it at the same time. Based on the app and the niche, what would you do in my situation?

I will continue with 3rd point before going back to the second point. Because this one here is the decision point. If you don't have time or energy (or passion), you probably shouldn't continue. If this feels like a drag, it means you chose an unaligned idea to focus. This is maybe one of the hardest things to change. You need to find a motivation to continue. Or find what motivates you and focus on that.

The following answers will assume you are doubling down on this idea.

I don’t know how to market the app. I did a couple of posts on reddit and people were interested, I had sign-ups etc. but not really a „break-through“. On the other hand, I was not doing any marketing/promotion besides these 2-3 reddit posts. Not sure, if I should continue due to #1. Any advise on who I could reach out for help?

How you should market this? The answer to that is "user research". See if you can talk with your users, steal an hour of their time. Ask them questions about (1) how they decide on an app in this domain, (2) what are the decision criteria for this kind of solution, (3) where and how they discover solutions, (4) how and where they search for a solution in this domain, (5) what is their "problem", what keeps them up at night, (6) how do they talk about this domain, what are the actual words they use?

If you can get answers to those, you will have everything you need. Including how to improve your product, where to promote, how to craft your messaging, what kind of positioning you need.

Although if your current users are not your ideal users, instead find a group of people who are more aligned with your ideal one and interview them.

English is not my main language. It is difficult for me to transport the ideas via e.g. the landing page or to create instructions/onboarding help etc. Would it make sense to partner with somebody who has the right skill set?

Partner up or outsource, if you have resource availability. Depending on what you need (if you only need documentation/sales copy, for example) partnering up might not be the best or only option.

My main intention at this point is to help people and to learn from them how to best support them on their journey. I thought, maybe I will just make the app free and see what happens in the next 12-24 month. Would people use this for free? Again, I would be more than happy if I could help people with their goals and dreams. Monetization is not even my main concern.

(emphasis mine)

The emphasised part is the right attitude. But it is not just about making the app free. It is about getting people to invest (their time) in it and get value out of it. People use apps in this domain for free all the time, no reason for your solution to be different on that.

But when it is free, there is always a certain issue around trust (will there be here tomorrow or will I lose every piece of data that I have on this platform? will they sell my data to used car salesmen? are they evil? if I say I am running a marathon will they try to sell me running shoes?). But those can be mitigated (but would require additional resources, like time and effort).

Here I will provide some unsolicited advice: if your focus is individuals, your app's name might not be the best one. "Mission Control" is too business-y for me. I'd assume it is a business KPI dashboard or something like that. Might be just me, though. Confirm with your current or ideal users.

Hey! If I were you, I would focus on 5 - promoting it, offering it for free for a period of time and just focus on getting at least 10 people (for example) to use your app. Then, I would focus on research. Talk to the active users, churned, etc. I think this will point you to validating your idea and your feature set.