Joaquin
First a few words of encouragement....
When I first started to learn about electrickery, I couldn't come to terms that ac current could flow back and forth fifty times a second, it seemed too fast. Now having spent more years than I'd care to mention in the electronics industry I have no problem with ac current flinging itself around at ten thousand million times a second (10GHz). Persevere it will come to you.
Try this analogy....
Forget about electrons, holes and other subatomic particles,they don't matter at the moment.
DC - take a battery, say one from a car. Connect two leads to it. Connect each lead to each side of a bulb. Direct current will flow from the positive terminal of the battery, though the bulb and then to the negative terminal of the battery. The bulb filament will get hot and glow. Bit like a water pump, pumping water around a central heating system. Cut one of the leads and the current flow stops, bit like hammering one of your central heating pipes flat. (Note that I didn't say you cut the pipe, this is why I don't like water analogies because although water would flow out of a broken pipe, electrons wouldn't flow out of a cut cable).
AC - take the DC set up. The bulb is lit. Now very quickly switch the leads to the battery. Current still flows from the positive terminal of the battery to the negative but the other way through the bulb. Because you switched the leads really quickly and you managed to do this fifty times second, the bulb filament doesn't get time to cool down and it doesn't flicker. As far as the bulb is concerned it is connected to an ac supply. Bit like reversing your water pump fifty times a second.
Hope this helps.