Finally it was not the solution 
I bought another screen and the problem remains…
I guess my problem is the pins soldering. See this post Noisy coloured pixels on my Fairphone 2 - #130 by ElKrasso
Tight now I put some paper between the backcover near the screen connector.
If it does not solve the issue in longer term, I will probably try to cook my mainboard sometime. 
3 Likes