1995 honda civic: What causes this and how to fix it pretty sure it's causing my misfire?

Something Is leaking into the 3rd cylinder only causing a misfire and lack of power it's like oil or something look at the picture what is it and how do I fix it thank you1995 honda civic: What causes this and how to fix it pretty sure it s causing my misfire

Pretty common. You need a new valve cover gasket and spark plug tube seals. The gasket set is about $40 and it takes about 1 hour to have it professionally installed. Or you can do it yourself. Just make sure you apply RTV sealant where the block meets the timing case. And use a torque wrench on the bolts and nuts. Overtorqueing is most common cause of leaks on new gaskets.