C is a fairly hairy language to get into, it's sure not the best learning language and unless you really need high performance there are other languages which will be better, C makes you do a lot of work you simply don't need to do in other languages.

If you want to learn "modern" OOP programming try Java, it's very powerful and does everything you'll need, it's also simpler than C. If you really want to learn C or C++, Java will provide a big head start.

Python is another, it's a scripting language but is also OOP. Looks very easy to learn as far as I can see.
I've never actually used it, I've done Perl (a lot harder to learn) but Python looks like Perl in English!
It doen't need a compiler so is easier to get going.

You could always try Python then move onto Java then C / C++, that'd probably be a good route.

That said I don't know if Python works on MorphOS, and Java doesn't work. It may be easier starting on a PC or Mac as both languages will work on them.