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)

"Recycled Sol LeWitt", conceptual artby Sebastian Bieniek (B1EN1EK), 1999

Conceptual art campaign by Sebastian Bieniek that led to the rescue of Sol LeWitt's "Cube Without A Corner", which was curated by Klaus Biesenbach and exhibited in KW, Berlin in 1999.

In October 1999 Sol LeWitt exhibited the "Cube Without A Corner" in the Kunst Werken (KW) in Berlin. Sebastian Bieniek, who attended the vernissage, wondered what will be done with the Sculputr after the exhibition.

When the exhibition was over, he swerved past the works of art on the way to his studio and couldn't believe his eyes. Workers were just starting to dispose of the "Cube Without A Corner" in the trash! Without thinking too much, Sebastian Bieniek broke into the exhibition hall, prevented the workers from throwing the work of art into the trash and took as much of the work of art as he could and thus saved it from destruction. Then he recycled the work of art and processed it into a multiple, the "Recycled Sol LeWitt".

Sebastian Bieniek is after the exhibition entering the gallery (KW) where "The Cube without a Corner" was

in 1999  in Berlin exhibited.

The gallery worker make breakfast and just don't care when Sebastian Bieniek is carrying the rests of the "Cube without a Corner" by Sol LeWitt away, 1999, KW, Berlin.

The gallery worker make breakfast and just don't care when Sebastian Bieniek is carrying the rests of the "Cube without a Corner" by Sol LeWitt away, 1999, KW, Berlin.

Sebastian Bieniek with the rests of "Cube without a Corner" by Sol LeWitt on the way

to his studio in Kunsthaus Tacheles, 1999.

Sebastian Bieniek entering with the "Cube without a Corner" by Sol LeWitt the Kunsthaus Tacheles, where in 1999 his studio was. It was the most famous "off-artist" house at that time in Berlin.

A few weeks later Sebastian Bieniek presented little pieces of "The Cube without a Corner" by Sol LeWitt at the Rundgang (end of the year exhibition) at the University of Art Berlin (UdK) in 1999 and offered them for 5 € each.

The in 1999 for 5 € by Sebastian Bieniek sold pieces of "Recycled Sol LeWitt" are now around

40 times more worth (around 200 €).