First of all, sorry of my very bad English!

How do I notice that I can't just talk in english?

When I still ask what is the difference between the pronounciation of eight, eighth and eighty?

I played in Google translator, and is changing so little that I just can't figure out, what is happening...

I imagine if I talk with someone that really speak English in high speed, and I will probably will think it is just "8".

Is this hard for native-speakers too, or just for a portuguese (Brazilian) speaker like me? Do you have some tip to learn something like that?

And if I go to different regions or English-countries, do I need to learn something more about 8, 80, and 8th?