troubled drive train need advice

my car used to accelerate well,now its laggy and barely gets to 5 mph in 1st gear,i have a front wheel drive man trans in an 07 toyota yaris, thought it was the clutch that needed replacement but didnt do the trick, what could be the problem

The first thing I'd do would be to see if any error codes have been stored in the ECM.
Around here auto parts stores will do that for free.
If there are any problems detected, the code will point you in a direction for troubleshooting/repair.