Note1 :

speaking a mile a minute

means speaking really fast

Note2 :

Be careful not to go overboard

Means (Do too much)

Here is the tip for your speed when you are speak English

Tip 1:

Make sure your pronunciation is nice and clear.

Tip 2:

Learn to think directly in English without translating.

Tip 3:

Relax about your mistakes and don’t try to be perfect.

Tip 4:

Practice shadowing regularly.