don't drop any subjects just yet, see how u go with them, u might turn out to like them and then ace them, and if thats the case, u'll do very well
do a little experienting, find what subjects u like, which one's ur good at, and which one's suck, even perhaps the subjects u don't need for future purposes
aftre this is taken into careful consideration, then u can drop a subject, discuss the matter, with parents, teachers, and siblings, cousins, etc....sometimes they know how capable u are of doing certain subjects like 4 unit maths and english
don't rush into anything to quickl, give the matter careful thought, but don't take too long either, otherwise ur marks may suffer as a result
however, if u can cope with the workload, then go for it
good luck, what ever choice u make