i wud keep the subject thats easiest for you
and dont decide on which subjects to drop just basing it on the usefulness at uni, thats why they have bridging courses
and atm doing well in uni isnt even ur main concern here
yea tutoring will help, to what extent tho will depend on the quality of ur tutor
its normal to be unable to understand the concepts on the first go so just give ur brain some time and u will get it eventually and i dont recommend dropping to general unless your foundations are rlly bad...