Hi TS,

Reading your post, I assume you are doing yoga alone? Issit?
It's the best when you can join Yoga studio so that someone can supervise your posture and provide assistance when your posture is a bit swayed/off.

Warm up is very important for a yogi before performing any yoga pose. Make sure your body has warmed up so that you can perform any pose. If you're stuck at certain pose, always start with the most foundation pose and slowly climb to that

There's a lot of tutorial on IG.
one of my fav is @yoga.tuts, it's important to improve with step by step.

Hurm, regarding knees and arms bruises, i normally get that when i do plank. perhaps, time to change your yoga mat or to put more comfortable material under your knees and arm.

I know it gets you excited when you unlocked certain poses, and when you're feeling stronger, and bendier than ever.
It's addictive.

Try to spend more time to activate your minor muscles and do longer stretching for warm up.
IG is your best friendsss haha.