as salam alaikum
there are many things a Muslim can do in his free time. Here are some suggestions:
1) Seeking religious knowledge by reading books and/or attending Islamic lectures, lessons and halaqat.
2) Learn how to recite the Qur'an and memorize it.
3) Passing quality time with his own family for the sake of Allah.
4) Attend good people, especially the religious ones by whom you can learn and practice more your religion.
With prayers for your success.