Text messaging has devolved into a huge mess of corporations competing with each other. Apple, WhatsApp, Telegram, Google, etc. all have their own different texting file type protocols that are a bad combination - they're proprietary and not compatible with each other. Despite PR statements otherwise, their priorities are not about providing a useful service to consumers, their focus is on short-term profit. We get screwed and they make money off of that.
So yeah, you're having problems with exchanging text messages between Android and Apple users. That is sadly a given, not something you have control over. Most iPhone users will be using the iMessage app, (using its iMessage protocol), so there is no equal option available for Android users. There is no such thing as an Android iMessage app, Apple's licensing won't allow it. So any Android text messaging app always will involve a lot of translation/conversion when it involves Apple's iMessage. Apple did make a big turn around recently. It will start to include basic support for Google's RCS protocol into its iMessage app. This might be a big game-changer. Just keep in mind that RCS is not an Open Source standard, it's a proprietary protocol owned and managed by Google, and Google's history with text messaging is a consistent disaster of canceled and dead standards and apps.
If you want to share media files without them being automatically scaled down, use email instead. Or use sharable links from your photos/videos stored within an online storage service (Google Drive, MS OneDrive, etc.). Email services don't have the same file size restrictions, but with some video content its safer to use sharable links anyway.