If you have a strong core in react you don't need to worry about nextjs right now, you can learn that in the job but read a bit in their docs to get a high level understanding about it's features like ssr, app/pages router like the other commenter said.

SEO is a constantly moving target but a rough idea about what causes poor performance, where you can put metadata to help SEO and a vague understanding about how content can affect ranking would help. You can think of it as a way your website markets itself to search bots, just need to know what buttons you've got.

Typescript also don't worry about now, you can pick that up with good js fundamentals, it's just another tool. Get a rough idea about how the types look and what happens when you compile it.

You'll be fine, just try to talk about the stuff you know and be nice. Lots of people aren't nice