When you add more mass does the friction decrease or increase?

Slightly increases

Explanation: Well, think about if you put more mass on something like you sibling on you and your going downhill. Do you increase in speed? Yes you do since you need more weight, so it’s then same as with friction! The more mass you put going down hill let’s say, will increase speed that increases friction since your at a faster speed!

not too sure thinking it will always be directed towards the centre of the earth. could be wrong not sure