Oh ya, that new prescription is doing wonder for my system.
If you remove the small caps covering the center holes of the binding posts, by using a very small screw and gently turn a couple turns at most by piercing the center of the small plastic plug, as to not damage your binding posts, and then by pulling out hard enough, so as to remove that small cap.
Quite easy actually.
To find out more about banana plugs, just Google "Speaker Banana Plugs".
Wow! 5 meters for your sub cable! Where do you put it? Outside in the balcony?

I bet you like to take care of your neighbours.
And as for the length of your speaker cables, just cut it to each their respective distance with an extra couple of feet just to be on the safe side.
Anyway, your two front speakers should have the same length. Your center speaker, probably shorter. And your two, or four surround speaker cables would be quite longer than the three front ones, duh.
(My two front mains are 12 feet long, my center is 6 feet long, and my two side surrounds are 25 feet long, and my two rear surrounds are 40 feet long).
Pretty much, more or less. Actually my left side surround is 40 feet long and my left rear surround is 45 feet long.
I also have another six speakers installed in that room, in addition of all the ones I just mentioned, so there are much more feet of speaker cables running around. The grand total of speaker cable feet woul be about close to 400 feet.

Just in that system alone. I got 4 more systems in my home.
So, I know that I'm way over 1,000 feet of speaker cables. Add all the interconnects, and I got enough copper to start a small copper factory.
And the two interconnects for my two subs are 10 feet (right sub) and 15 feet (left sub) long, in my main system.
So, just use what you need, no more (or just a couple more feet) no less.
Bob