My friend tends to lie. He is good at physics or is the best physicist at my community college in my opinion. However, he likes to lie a lot. When I ask him for help, he always says something along the lines of "I'm stupid and not that smart" or you should ask _____ for help, he is smarter than me. He calls himself stupid, when he was a valedictorian, which is ironic. While the second might be true because subjectively to me he is the smartest in physics, but to the teacher or other students my friend might not be the smartest, the first statement is a flat out lie. What would I describe this type of behavior where they purposely say they suck even though they do not, and I also believe he deep down believes that he is smart/hard-working. I would not call him humble, because of what I said above where I truly think that he believes he is smart. However I do not think liar or jokester is the right term either. When looking up liar, I found a word that started with a word that started with an m that meant he was a great exaggerator. However, I believe he is the opposite, where he greatly downplays the significance of something, in this case his ability to solve physics problems. What word would I use to describe this behavior. To me it seems like a false humbleness.
P.S. In case you were wondering, he does help me with my homework but not without some "joking" about how bad he is at physics. Also, I said he was a valedictorian because this/last semester he got his first B.