If your toilet isn't flushing properly, there is likely a clog in the pipe. You can use a plunger to attempt to move the clog through the system.
Drain and Shower Clogs
If your sink or shower isn't draining properly, there may be debris clogging the drain pipe. Many hardware stores sell cleaning tools you can use to fish debris out.
Please don't use harsh chemicals to clean the drain, as these could damage the system.