Puppy won’t play without bitting

A week ago I adopted a 7 month old border collie sheppard mix. She is amazing and everything i could ask for, sleeps through the night, crate training has been easy, does chew things up. However she play bites a lot. She was a stray and spent some time at a shelter so most likely didn’t get proper training early on. The affectionate nibbling when she’s excited and were cuddling are just a mild annoyance as i can hide my hands. However she’s extremely high energy, we take her out for 90 minutes to 2 hours of walking a day along with at least 20 minutes of playtime and if we have time a training session.

Playing fetch and tug seems to be the best way to get her tired out. However she likes to bite my arms while we are playing. My arms are covered in bruises and these are not gentle bites (never drew blood but still hard).

Things we’ve tried:

• Tiring her out as much as possible
• Stopping playtime when she bites too much
• Trying to prevent her from jumping up (unsuccessful)
• Rewarding good play
• Holding her mouth shut
• Scolding her in a stern but not yelling voice

I know it hasn’t been long but i’m wondering if we need to stop playing fetch and tug until she is better trained. She has tons of toys and should be done teething so i think she just thinks we’re playing.

If anyone has any advice I would appreciate it as i’m starting to dread and almost fear playing with her which i hate. It’s really tough since she can jump about 5 feet into the air and runs very fast so trying to be defensive only works sometimes.