One of the first questions I get asked when I meet someone new in the Czech Republic is:
“How long are you in Czech Republic?”
This needs to be in the present perfect as it started in the past and the result is now (because I am still here), so you should say:
“How long have you been in the Czech Republic?”
Top students will also notice that it is THE Czech Republic. The only way you can shorten it is by saying Czechia.
My answer is: “I have been here for just over one year.”