Totally agree with you

I always promoted the muscles theory for the pronunciation. As long as your tongue, mouth and lip in the right position, you cannot get wrong. The problem is sometimes, even we know the right position but muscle is too weak to do that. So over exaggeration is necessary in the beginning. Slow as much as you can and pronounce every vowel and consonant correctly. You will benefit from it in your life time. I was told by my tutor one year and half ago.

Your intonation is very good. But there are some stress issues.

A few words for your reference:
under /der/ is missing
spoke souds like /spoke/ rather than /spouke/

Good job!