This is probably bad, but I've never pronounced the 하 syllable in 안녕하세요 and 감사합니다... Because I couldn't hear it when I first started learning. Now I do hear it, but I can't change my own pronunciation. I just draw out my ㅇ or ㅁ sound, respectively, for an extra long time lol...

But since no Korean person has ever corrected me on those words... if a friend asks me how to say "hello" or "thank you" in Korean I actually don't teach them to say 하 either. Haha. Not a liberty I should really be taking with a language that isn't mine, but it's definitely the least important syllable, right? If you can remember the other 4, then Koreans will still understand what you're saying, and that's the important part I think lol. (I am also hard of hearing like OP)