I'm a beginner in French so these questions may sound really stupid. I apologize beforehand.

So first, if I want to say <today is>, then shouldn't it be <aujourd'hui est>? I've seen many people say it has to be <aujourd'hui c'est>, can someone explain if both are correct or only the second one is?

Secondly, I was trying to write the sentence <I met new people>, so I wrote <J'ai recontré nouvelles personnes>. But a person told me there has to be a <de> before <nouvelles> and after <recontré>. Can someone explain when do we have to add a <de> after verbs?

And lastly, about the gender, say I'm trying to describe a male cow. The term <vache> is feminine, but the gender of the cow I'm describing is male, so should I say <un vache> or <une vache>?

Thanks in advance!

PS French is hard