“Give me 5 min.”
Your friend texts you asking if you can chat on Skype. You just need to finish writing an email and get some water. You ask him to wait a bit.
Give me 5 min.
When you ask someone:
Can you give me a minute?
...you are asking for them to wait for a short length of time.
You can also say why you want for them to wait:
Give me a few minutes to catch my breath.
When you're writing casually, you can use abbreviate "minute" or "minutes" to "min".
Classes last 30 min.