Question

mohsin runs (fast /fastly)​

Answer 1

mohsin runs fast

hope it's helps u

Answer 2

Answer:

Mohsin runs fast. Sometime some English learners are also using the word fastly as  an adverb of the word fast.

It appears to be logical. This is because in this way the adverb which is formed appears natural to the ear.

It is like moving "slowly".  So fast or fastly both are here falling under the catgory of the fall.

Explanation: