Learn Dutch: Alles wat u zegt, fascineert mij. - Everything that you say fascinates me.

In Dutch, when you refer back to an indefinite word like alles (everything), iets (something), or niets (nothing), you must use wat as the relative pronoun. You cannot use dat or die after these specific words.

Why is the word order u zegt instead of zegt u?

Because wat u zegt is a relative clause, which functions as a subclause. In Dutch subclauses, verbs are pushed to the end. Therefore, the subject u comes first, followed by the verb zegt.

Why is there a comma before fascineert?

The comma marks the end of the relative clause (wat u zegt). The entire block Alles wat u zegt is actually the subject of the main sentence. Because the subject contains its own verb (zegt), a comma is used to clearly separate it from the main verb (fascineert).

Could I use me instead of mij in this sentence?

Yes, you can. mij is the stressed form, which puts a little extra emphasis on the fact that it fascinates you specifically. If you just want to state the fact without that extra emphasis, the unstressed form me is perfectly fine.