It's not all episodes of Jojo's bizarre adventures on Netflix, are they?

As I only know the first 2 parts, how many episodes does Jojo's have in total?

Netflix has three parts (episodes 1-74)

Part 1 → 9 episodes (Ep. 1-9)

Part 2 → 17 episodes (Ep. 10-26)

Part 3 → 48 episodes (Ep. 27-74)

Part 4 → 39 episodes (Ep. 75-113)

Part 5 → 39 episodes (Ep. 114-152)

The seasons at Netflix and Co. Are divided differently than the parts, namely as follows:

Season 1 → 26 episodes (Ep. 1-26) - Part 1 and 2

Season 2 → 24 episodes (Ep. 27-50) - 1st half of Part 3

Season 3 → 24 episodes (Ep. 51-74) - 2nd half of Part 3

Season 4 → 39 episodes (Ep. 75-113) - Part 4

Season 5 → 39 episodes (Ep. 114-152) - Part 5

You can watch Part 4 and Part 5 or All Parts for free and in full on Crunchyroll.

Many Thanks. But I can just continue to watch Netflix as normal as it is divided there, right? So the order is the same, so I would only have to look at Part 4 & 5 elsewhere.

Yes, you can just watch all episodes on Netflix and then watch Season 4 (Part 4) and Season 5 (Part 5) on Crunchyroll.