Building a wall, how much is 7 cubic meters...

Mixing 7cbm of concrete is quite a challenge. I would order ready-mixed concrete delivered by truck. With a few helpers, wheelbarrow unloading is also possible, but it costs extra. Otherwise, use the concrete recipe for standard concrete, you can definitely find it on the internet.
Regards

I was asking about the 7cbm bins, how much gravel/sand?

Is the rule of three already too difficult? When is it taught? 4th grade? 5th grade? It used to be called word problems.

Necessary information can be found on every bag of cement or on the internet.

And the conversion tons/cbm will be done for you by the appropriate supplier.

Concrete mix design states how many kg of aggregate, cement, and water are needed. Then it can be converted into cubic meters according to the bulk density of the individual materials. I know the density of water by heart: 1kg/dm3 :-)

is that complex