What is the difference between "Performance", "Action Art", "Installation Art" and Video Art? 

When the artist or the body of the artist is in focus, so the acting is part of the artwork, it's a performance. When the artist isn't visible but it's still about people and when it's that fast changing in time that you can see the "Beginning" and then "End", than it's "Action Art" (Happaning is kind of outsourced - not directed by a single artist but by many). Installation is when you can't see it "changing" in time, so it looks always the same, or can be at least restored, and when it's about objects.

However even still some installations like "My Breath rests here" ("Hier ruht mein Atem") have some performance character (at least in the creation phase), but than again not really, because than "the painting of a painting" could be also a performance, so it's more about the focus. Or take the (big) "Please Ignore This" from 2018 and compare it to other Bieniektext textart. What's the difference? It's only the size.

A recorded and shown as a video performance, without real life viewer and the interaction with the viewer like "The 30 € truth" or "Crying for this Video" for example is a video.

What is the differance between Installation Art , "other conceptual art" and sculpture?

Installation is somehow big. If you can't carry it away it's an Installation.

If it's small enough that you can carry it away and when it's technically not unique (so you can't recognize a signature by the making, or - even - somobody else did it, like the "overpainted Sebastian Bieniek") but - may be - by the "spin" of the idea, than it's  Bieniek's "other conceptual art".

And than: sculpture is when it's made by the artist himself and one needs a little "artist like" skills to do it, or at least everbody would do it kind of different, but this "different" was made by the artist himself.

Nevertheless some artwork like "Recycled Sol LeWitt" , or the "The Stolen 100 DM" are still hard to collate. What is it? At the beginning it's "Action Art", than depending on the presentation, it could be an Installation (if you take a lot and make it big), and if you just take (one) the final result could also be a sculpture, but according to the definition "without special skills and skill-signature it's other conceptual art, it's "other conceptual art.

(Bieniek's definition)

  "Bag Tree" ("Oh Tütenbaum"), Installation art by

Sebastian Bieniek (B1EN1EK), 2000

Installation with 400 supermarket bags on a 40 meter cedar tree. Saar-Palatinate Art Prize, Bexbach, city gardens. This work is an allusion to commercialization. The original German title refers to the best known German Christmas song  ("Oh Tannenbaum"), which is a symbol for the takover of commercialization.

 "Bag Tree" ("Oh Tütenbaum"), Installation art bySebastian Bieniek (B1EN1EK), 2000.