Need help with subtitles on screen mirroring PLEASE

Okay I really need help with this like ASAP it’s driving me insane. I use a few anime streaming sites on my iPad and screen mirror it to my tv. And it works great the only

Problem is that for some reason as soon as I put on full screen the subtitles disappear??? This happens with every website. And I don’t know how the heck to fix it. I can zoom in on my iPad to fill the tv and the subtitles stay but it makes me so mad how still not the whole tv screen is used and I can still see the borders from the website. And no I can’t stand watching dub and need a fix to this please. I use safari or brave and it does the same thing the second I go full screen mode. How do I fix this?????? If it’s complicated please respond like you’re talking to a 4 year old I’m not very good with technical stuff I just stream on my random websites and that’s it. Oh also this seems to only be a problem with anime? I use other sites for regular tv and subtitles don’t go away on full screen just the anime websites. Please help.