Will need more information to assist you.

First, what Nostr client are you using? Also, what media hosting service is set up for uploading to?

Relays don't store videos or photos, so Nostr clients upload those to media hosting services, such as Nostr.build. Those services typically have a maximum file size, especially for free uploads. For instance, Nostr.build's max size for free users is 100MB per file.

As for a client that is similar to YouTube, Nostr doesn't have any good options yet. The media hosting problem had to get resolved first, and we're just barely getting there with Blossom protocol and the ability to split large files into smaller pieces for faster retrieval and loading.

I would not be surprised to see a serious attempt at a YouTube replacement in the near future.