I have always hated present perfect.  :p 

I have worked in a foreign country.

I have studied English...and I have almost forgotten it! [emoji]

Sudeep

Yes, it's possible, but you need to give more in your sentence. What I mean is, if I say on it's own:

"I had been skiing for a month."

An English speaker will probably say:

"And? Finish your story!"

We usually use the past progressive in conjunction with the past simple. For example:

"I had been skiing for a month before I learned how to stop"

or

"I had been living in Germany for a month when I met my girlfriend"

If you want to just say that you were living there for a month, then past simple or past progressive are the best tenses to use. And, actually, the past simple is the most correct in this case.

I imagine the conversation being something like this:

"You speak German so well!"

"Thank you. I lived in Germany for a month"

Excellent stuff! Well done all!

I don't think you have almost forgotten how to speak English, you can obviously use the present perfect!

I hope you enjoyed your cup of tea Mohmd :)

And yes, Sudeep, I have eaten octopus, it was quite tasty! A little strange for me, as I am not used to that kind of seafood, but really very nice.

With the present perfect progressive we can also say things like:

"I haven't been exercising enough recently"

This means that at some point in the past, I started not exercising enough, and this situation continues at the present moment.

or

"John hasn't been doing the housework"

This means that, at some point in the past, John wasn't doing the housework, and this situation continues in the present.

With the present perfect simple, we can use the negative too and say things like:

"I haven't been to Brazil"

This just means that at no point in the past have I been to Brazil. We still can't use specific times with this tense.

Or, we can say:

"I have never ridden a horse"

and this is the same as the above case. At no point in the past have I ever ridden a horse.

The main thing to remember is:

Present perfect simple = used for something that happened in the past at an UNSPECIFIC time.

Present perfect progressive = used for something that started in the past and still continues.