Hi! I think it is worth checking if you might have
anterior pelvic tilt, as those tend to go hand in hand with
flat feet, overpronation and forward neck posture.
This normally means there is also lower back pain, the chest seems to bulge a bit more, the abdomen seems more "swollen".
If this is not the issue, and the flat feet are due/causing other problems, you might have forward shoulders too, almost like guarding your head, similar to the guarding boxing punch posture, as well as knees and femur going into internal rotation (
feet and knees seem to point inwards, instead of to the front of you). With
anterior pelvic tilt, leg raise exercises might be quite painful without supporting your lower back too, so check for the signs.
It is very difficult to assess your specific situation just by a post, but there is a
good video that seems to cover what I am trying to explain and provides
examples of exercises to fix it. (This is not sponsored or promoted. I just watch this dude from time to time, as he seems to know his stuff).
If you definitely identify with the anterior pelvic tilt too, you might benefit from
this darebee hip flexors' stretch.
Core training might be also fundamental then to help balance things out.
It is also worth considering buying some
special shoe insoles for flat feet.
Two pairs of these are covered normally by the GKV (if you have it) per year.
Your GP Dr (
Praxisarzt) can prescribe
Krankengymnastik too, and it is often also
covered by the GKV (in blocks of 6 units). I think you might need to pay 10 euros plus 10% of the treatment cost though. I think you might also be entitled to
Manuelle Therapie (MT), but that tends to cost around 20-25 euros for a 6 session block.
On addition to that, your
Krankenkasse might offer f
ree online coaching or certified
webinars on workplace ergonomics that might help with the neck specifically.
Lastly, if neck stretches provide relieve, keep doing them, but I personally don't think it will fix the root cause.
I hope this helped! Take care.
EDIT: provided bold text for key bullet points to facilitate a quick reading.
Also, my post is not medical advice, just a personal recommendation.