Your breather hose MUST be open.  Remove the cap/plug.  The breather system ventilates your crankcase.  Your crankcase will pressurize with that hose plugged/capped.  Instead of a plug, you need a small breather filter in the end of the breather hose.  Air flows out of the hose when your piston moves down, and flows into the hose when your piston moves up, hence the breather nomenclature.

The fact that you have fuel coming out of the breather hose indicates that your crankcase is fouled with gasoline.  This is a common problem usually related to the stock petcock. But I can see you do not have a stock petcock, so I assume either your petcock is leaking, or you are leaving it turned on.  Check your petcock to verify that when it is turned to the off position zero fuel comes out of the fuel hose at the carburetor.  Once you know the petcock does not leak, make sure that you ALWAYS turn your petcock off when the motorcycle is not in use.

Your oil is contaminated with fuel.  You need to dump the oil and refill to the proper level with new oil.