I must be doing something wrong. I changed the gaskets of the bevel gear and part of the crank casing of the stator. But after replacing the gaskets they kept on leaking oil. Is there something im doing wrong?

Also for the crank casing I broke off the lower right bolt and part of it is still in there. Is there any easy or safe way to get it out? I notice when looking up pictures for the bolts that sometimes a blue plastic like substance is on there, is this for preventing leaks or should a gasket be enough?