Tutorials on mixing might be helpful. My guess is that the levels on everything are so hot that the 808 is crushing your mix. Watch your level meters on the main volume. If they are going in the reds, bring each individual track down the same amount, say 10 percent. Keep doing that until the overall track is out of the reds.
Basically if you are taking what was already a full track and adding an 808 without making room for it, everything will get crushed and sound like **bleep**.