I can read arabic however very slow. I have an app on my phone where it has all duas and ziyara’s. Is it permissible for me to ricite them in english rather than arabic? As I will understand what I'm saying and also i can read long duas fast and they will be understandable.

I am also going arbaeen this year inshAllah, is it permissible to recite ziyara aashura or ziyara arbaeen in english rather than arabic?

The answer is yes to all the above