i agree with him but only if you have a very very bad cube like a rubik's brand or something like that. other than that if you want to buy a new cube go for the mf3rs of little magic . they are great budged cubes. you might need a good magnetic cube when you are around 18 seconds.
you are soooo like me.Some time ago i also had a PB of 27/28 (now it's 20) and my average is the same as you in 3×3 and 4×4 as well.I also have the same puzzles as you with a 2×2 more than you.Where are you from ?
Once a noncuber said to me that he could solve a Rubik's cube. Then i gave him a scrambled cube. He started to do R and U moves and said "After i do this several times, the cube will be solved"