Hi @AMIRMOHSEN ,
Thank you for posting on the Instructure Community!
When it comes to using canvas on your laptop for your two schools, I recommend bookmarking them so you can easily switch back and fourth as you please. However, with the mobile app, you will have to sign out, and sign into your other school's canvas instance, there's no way to access both of them on the mobile app at the same time. The mobile app will usually save your previous logins though, so it should make it easier for you to go back and fourth.
I hope this helps a bit, reach out with any additional questions! Thanks.
Noah