Student or Learner
Which one is good to write.
You can go to the store anytime or You can go to the store any time.
What is the difference?
No difference. Some sources tell you that "anytime" is informal, while "any time" will work in any context, formal or informal.
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.