'Câmpul electric creat de o sarcină electrică q punctiformă plină în interior, în repaus, este...'

Literally, 'plina in interior' translates as 'full inside'. My assumption is that the author is trying to be poetic and that what he actually means is that the electric charge is positive, otherwise it doesn't really make much sense.
'sarcina electrica q' - In physics, the symbol for electric charge is q and so this translates as 'the electric charge, q'
'punctiforma' literally translates as 'punctiform' but in this context, he refers to the 'point charge', which in physics is a hypothetical charge located at a single point in space.

And so the translation is:

'The electric field created by a positive point charge (q), at rest, is ...'

I hope my explanation is helpful.