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)

 "Phoenix Paintings", conceptual artwork by Sebastian Bieniek, 1999.

Works of art made from the ashes of other works of art (paintings) by artist.

These three works are made from the ashes of the paintings that Sebastian Bieniek burned in 1998 (see "Burning Paintings" performance).

The artist burned his own paintings in 1998 and afterwards mixed the ashes of these paintings with glue and processed them into a new form, the form of conceptual art.

On each work is written the title, size and technic of the previous painting the ashes were from.

"Phoenix Painting No. 1", Sebastian Bieniek, 1999.

"Phoenix Painting No. 2", Sebastian Bieniek, 1999.

"Phoenix Painting No. 3", Sebastian Bieniek, 1999.

The entire "other conceptual art" oeuvre is, in a very specific way, a kind of resurrection oeuvre.

Every artwork from this oeuvre, from the very first one which is "The Turning around Drawing" (a circle of again and again) to "The Phoenix Paintings", to "Recycled Sol LeWitt", to "The Stolen 100 DM", to "Overpainted Sebastian Bieniek", even "Bird Shit on Gold", is telling the story of to fall and get up again and again.