Hi,i have been lifting for 1.5 years and i got a little bit problem with my ulnar nerve.i dont feel any pain or something.i just feel some numbness in my arm.if i improve my forearm extensor and triceps muscle,does the pressure on the nerve decrease?

You may have the condition "ulnar nerve entrapment". With this condition, improving those muscles will not help the condition. You should see a neurologist or orthopedist for the advice.

Perhaps you do have nerve compression at your elbow causing numbness, and this may be mild. But you cannot solitarily manage this and you need EMG testing to confirm, localize, and objectify severity. It may be that your muscle building has lead to this consequence and further lifting is not going to improve if that is all that is accomplished. See a neurologist or physiatrist.