Can I improve my intelligence now while i am at the age of 24 years old and approaching 25?

I am an electrical engineer with 2 years of experience, in the past at school and early college time i used to be very smart and distinct among my colleagues but later (since maybe 4 years ago till now) i noticed my smartness severly decreased, i lost my ability to think properly as before although my knowledge is increasing but my thinking and creativity capability is decreasing !!! is there anyway i can do now to develop my smartness & intelligence again while i am at this age ?