Compared are the Syndicated Version (available on the US DVD) and the Uncut Version (German Free TV).

In the US, footage of any episode has been removed so that the network had the opportunity to extended the commercial breaks. These TV Version are called "Syndicated Versions". The US DVD Boxes only contain these Syndicate Versions for some reason.
8 removed scenes = 121 seconds

1.11
The last shot Willi right before the beginning of the credits is missing.
4 sec

1.12
The main theme is slightly different. In comparison to the Uncut Version, the Syndicated Version contains a slightly modified version of the main theme. Furthermore the shot of ALF's attempt to get some cake is missing. He reaches for the cake in the fridge but Kate slaps the top of his hand to withhold him.
6 sec

2.03
Different shots of the Tanner's house after the credits in either of the versions.
no difference
left: Uncut Version / right: DVD

8.42
After ALF asked Willie to speak to him, the Syndicated Version is slightly longer, then it fades to the next scene. The Uncut Version also contains the following:
Willie says he spoked exclusively to him. ALF replies he was going to rebuild the garden as it had been before. Willie wants him to do it asap. ALF says to Kate Willie seemed to be a bit upset. He tells her to start digging and he was going to talk to him. While Kate is leaving, he explains to her he was fine with her talking to him because he would at least listen to her.
30 sec

12.19
Missing shot of the residents on Gilligan's Island and ALF. The residents tell ALF what the others are doing the entire day.
16 sec

12.38
ALF asks Gilligan why he'd never asked Mary-Ann out but Gilligan doesn't understand and asks ALF where they were supposed to go? ALF starts laughing again.
16 sec

14.06
The Skipper says he'd wrecked once and he'd be confrated with that over and over.
5 sec

14.49
ALF tries to motivate the other to sing the main theme from "Gilligan's Island" but they don't want to. Meanwhile Gilligan calls the Skipper big and fat. The Skipper replies Gilligan was going to have his big fat fist in his face in a couple of seconds.
30 sec

17.12
Some more missing dialog. Gilligan recognizes Willie's new shirt.
14 sec

Ironically the final credits of the Syndicated Version a short scene of ALF singing the Gilligan's Island main theme which is, as mentioned before, missing in the actual episode on DVD.