4cyl diesel leaking oil help!

[mortalidiot]

I have a 1982 mercedes benz 240D it looks as if it is leaking oil from a couple of places, but I could almost put my money on it it is because where the airintake goes into the camshaft if thats what it is called and that little hose right there is very loose I am not very familiar with engines and dont know how to operate the hose clamp to tighten it I think it could be leaking oil from just that one place and then being distributed throughout the engine. It also looks as if there is a little in the air filter casing. Also if someone could tell me what the round cylinder between the two connecting them what that is it would help also thanks.