Verified answer

Not at all.

the second verb doesn't have to be an infinitive. Adding an infinitive is like adding a direct obejct:

I like to do = I like the fact of doing...

And that's not what you want. In your ccase, you're using a gerundive (ing), so you should have o use "j'ai été practiquant"

BUT THIS STRUCTURE DOES NOT EXIST IN FRENCH. You should know that the translation for "to be + ing" = "Être en train de + inf"

I'm playing = Je suis en train de jouer.

You can apply this to the past tense, but the imperfect already denotes this continuity, so you can use the imperfect tense for all these cases in past. Hope I've helped.

Nope.

I was practicing is je practiquais.

No. What you "know" is incorrect. You are trying to use the passé composé, and what is wrong is that you have said: I have practiced for my concert.

The Passé Composé is the present tense of avoir + a past participle.

(I had been practicing would be J'ai été practicante).