How can one deal with a friend who always likes to be the best and who knows everything?

Islam calls for humility and shuns arrogance. The Prophet, peace and blessings be upon him, said: "No one who has a mustard seed's worth of arrogance in his heart will enter Paradise." Arrogance was defined as "rejecting the truth and despising people."

If your companion is arrogant, you should advise him and remind him of its consequences. If he does not desist, there is no harm in forsaking him if there is a benefit in doing so. If it is not arrogance, then be gentle with him.