Q: how can i clean my mac...seems to be slow

Don't buy any supposed "cleanup" apps.

They are good for lining their vendors' pockets with gold.

How much free space do you have?

How much RAM does youe Mac have installed?

Allan

See:

Mac Maintenance Quick Assist,
Mac OS X speed FAQ,
Speeding up Macs,
How to Speed up Macs,
Macintosh OS X Routine Maintenance,
Mac troubleshooting: What to do when your computer is too slow,
Essential Mac Maintenance: Get set up,
Essential Mac Maintenance: Rev up your routines,
Maintaining OS X, 
Five Mac maintenance myths and
Myths of required versus not required maintenance for Mac OS X for information.