@Frieda: I’m glad this has been at least a little bit helpful for you I’ve actually found a couple of topics that are quite similar to my problems. They don’t have any answers either, but I’ll link them anyway if you’re interested:
If for some reason you don’t want to ask for a new phone with the warranty, I’d recommend trying out a different operating system. Lineage OS really helped me, and one of the people in the topics linked above. Even though changing to Lineage didn’t solve the problem, it has made my phone a lot more reliable and useable. It might be a bit difficult to do by yourself, it was pretty tricky for me at least. So maybe ask a friend/fairphone angel to help if you can? If you want to switch to Lineage and don’t know where to start, ask me and I’ll give you some links that helped me with the process!
@JeroenH: Not sure if you’re asking me or @Frieda, but I’m not using one.
I’ve actually found a couple of topics that are quite similar to my problems. They don’t have any answers either, but I’ll link them anyway if you’re interested: