Question about Arctic Silver Thermopaste silver 5 (3.5g)

Approx. 1 gram is enough for a CPU. As a rule, you underestimate the Mende and apply far too much. But a wafer-thin layer (according to the Internet 0.3 mm) is enough. The surface is smooth, it's just a matter of smoothing out the irregularities that are not visible to the eye and ensuring that the metal surfaces stick together so that there is no air in between.
I apply a small amount in the middle of the CPU (about half of a pea). Then I press the cooler onto it and take it away again. You can then see how the paste has spread. If the heatspreader is not completely covered, apply a very small amount again and then mount the cooler.
You can also spread the paste carefully, e.g. with a piece of cardboard. You will then immediately notice if you have applied too much. If the paste runs over the edge of the heat spreader, it is too much.