HELP:::: PLS got few problems with my italjet torpedo 125cc

hi i hope some1 can help and explain things to me i have a italjet torpedo 125cc 03 plate scooter problem number 1 is i have lost speed whe i first got the bike i cud get 50-55mph out of it but now can only get 45mph max second problem is i need to clean the carb out i think but sound really hard if some1 cud pls explain it to me simply how to do it ill be fine pls help it driving me mad