text messages

I have a Samsung Galaxy S20. Sometimes, when I receive a text message, it requires a download which says "No subject." When I click the message, it appears to be downloading but eventually it errors out. I think this has to do with receiving messages over a certain character limit. I tried...

Hello. (Samsung Galaxy S7) All of the sudden this black bar appears at the bottom of my screen, ..it's a little bit over 1/8".....it doesn't bother me except can't see bottom of the icons on text messages and a few apps. My phone and battery are fine, and internet is fine except this black bar...