I can't get deep into my squats.
What stretches or exercises can I do to increase my mobility?
>implying I can even have my feet flat while squatting
>>41843753
Have you tried lifting less weight?
>>41843753
Check your form.
Avoid doing this on /fit/, but find a decent bodybuilding/powerlifting forum and post a video of your squats, they'll be able to point out issues.That's assuming you don't have a bro who is qualified to help in person.
As for mobility, just squat. Keep squatting, even with just the empty bar, until you can do it properly and it feels natural.
Also, don't put too much weight on, hence why I suggested the empty bar. Most form and mobility issues are caused by lifting too heavy too soon.