Chosen Solution
I jumped on the pool with the phone with me. Because a week ago I had to repair the screen myself, the water protection was not there anymore. After using it for 1 hour the screen turned off with an increasing purple filter. I was able to turn the device. After it, I opened it and saw the damage done by the water. There was plenty of water. I disconnected the battery (and remove it) and put the phone on alcohol isopropanol. After few days drying out with silica gel (for the water). I replaced the screen and it worked since I put the sim card. It seems out the cellular data is being connected and disconnected all the time. Every 10 sec the data is disconnected and after 10 sec the data is connected. When I call someone everything seems fine. No discconection at all.
Because water is trapped between the layers of the board and ruined the motherboard. This is going to be a very expensive or extensive repair.
It might be the sim card reader is damaged,if so you need a new logic board.¯_(ツ)_/¯
