Contract says I assign copyright to the company. Is it possible/legal?

Take a look at [1] and think about your situation. If you still feel that the contract is problematic, you could ask them to further clarify what the assignments apply to. But the general idea is that they want to own the thing(s) they paid you to do for them. As long as other stuff doesn't get caught up in that agreement, it's completely fine.

[1] https://en.wikipedia.org/wiki/Work_for_hire

There's a couple of things to this: first, copyrights can be transferred (eg, sold or given away). [1] Second, in the context of work done on the behalf of others, there's a distinction based on whether or not something is considered a "work for hire". In WfH cases, the initial copyright belongs to whoever paid for the work to be created. This article[2] explains it better than I can.

copyrights for everything I do during employment in the name of employer.

Note however that "work for hire" has a very specific meaning which is defined by law. It does not mean "everything you happen to write while employed by a particular employer". So if you're employed as, say, a software engineer, and you write a novel in your spare time, that would almost certainly not fall into the "work for hire" category.

Note some employers still try to get employees to sign agreements that are so broadly worded as to make it possible to argue that they could try to claim your novel. Those agreements, that go beyond the obvious "stuff you do for your employer belongs to your employer" level are the ones to be wary of. Further note that whether or not such an agreement is enforceable depends largely on state law (in the US).

[1]: https://www.copyright.gov/help/faq/faq-assignment.html

[2]: https://www.spear-ip.com/blog/difference-between-a-work-for-...

I'd say it's pretty much standard. Copyright is a form of IP and thus companies usually require you to assign it to them. It'll probably come up in every future due dilligence.

I don't know whether it's enforceable, but I think it probably is — for work connected to your employer, at least.