Yes, you can surely complete class 11 syllabus in 3 Months.

You just have to properly plan your day and complete syllabus accordingly.

For theory, you can go for one shots videos of Roshni Ma'am.

https://youtube.com/playlist?list=PLCzaIJYXP5Yf57bld-sUTSD2-aCEejZqb&feature=shared

And for NCERT Solution :

https://youtube.com/playlist?list=PLCzaIJYXP5YfGyNMhftfiUAh4aTyj_AMk&feature=shared

These are for Maths. You can also find for other subjects on our channel.

And depending on the numbers of hours of the content you have to study, you can plan your day.

I hope it helps.

Please contact if you need any help from me.