One difference between C and Pascal is that the 'typing' (as in data types) and memory handling is a lot looser (and therefore more flexible) in C that it is in Pascal.
So it is easier to get into trouble re runtime errors with C/C++.
So just take it slow and build up your skills gradually.
If it takes you 12 months or more to really get a handle on C then so be it.
But my experience is that the hungrier you are to learn the faster you will pick it up.
Part of the process of learning a programming language is a bit of brain wiring re-organisation.
You have to gain the ability to break down a process, that you innately know how to do with little mental effort, into a series of logical steps that you can represent in code.
Something as simple as print "HELLO WORLD" 10 times. Very easy to do this on a piece of paper with little thought. But how do you make a computer do it with C.
This will be the biggest hurdle for you, but patience and perseverance will pay off in the end.
There's nothing to say that you should restrict yourself to a single language though. Indeed, you'll find you will understand programming much better once you're familiar with several languages.
Well, if he is learning a programming language for the very first time then it is best to concentrate on one, and on only, until he is confident with it.
THEN is is easy to learn others and switch and swap between them as needed.