after a while, I found out that the microphone doesn't work. I can't use duolingo, for example, and the phone app works only using speakerphone. There are apparently two microphones, the top one seems OK, I believe it is the bottom one which has the problem. I'm thinking that I may have got some adhesive in the wrong place down on the bottom left, and wondering whether I should reopen it and look, or just leave it alone and live with it.

Thanks to all, everything went well. I repaired a screen on a samsung some years ago, successfully, but when the screen got wet in the rain, the phone died. Obviously, the waterproofing failed, so with this phone, I'm going to buy a waterproof case.