A bent rear sprocket is often caused by a soft tire. Remove the rear tire. Remove the four 10mm bolts that hold on the rear sprocket. It is sometimes possible to straighten the sprocket. Otherwise replace it.
Fork is bent.
To preserve your fork keep it tight and do not do jump or hit bumps. To install a new fork remove the T-bar and wedge as described in the handlebar section. Remove the gold and silver washer rings and pull the fork straight down. Remove the front wheel. Save the bearings unless you have others.