Hi Willy. Welcome to the World of TI. It sounds like you have made an organised and purposeful start to your swim practice which is great.
Many people self-coach very successfully (there are lots on this forum) but there is also great value in having someone on poolside to give you feedback from time to time. It's not going to be so easy for you to hook up with a coach or get along to a workshop as I don't think we have these in Germany yet (watch this space though!!). You are always welcome to attend a workshop in the UK of course - they are held very close to Heathrow Airport!!
However, what a number of swimmers have done is to get someone to shoot some video of them swimming (both above but most importantly below the water) and post this on the forum for feedback.
That way we can see how you are swimming and provide more specific feedback on drills and focal points which will be of most benefit to you.
If you are comfortable with doing this you will get a lot more insight into your stroke.
It is also useful to view video of yourself swimming as what you 'think' your are doing is often very different from what is actually happening!
The main thing to note though is that you are not alone. TI is global! So there are likely to be other TI Swimmers in Germany who are close by who you could meet up with.