I think your friend is on to something telling you to make the mountain elevations more sharp and jagged because yeah, if nothing else it will help differentiate them from the rivers. One thing you could do to is add even MORE lines, even finer even smaller, branching out from the 'secondary' lines, to represent valleys (like example 3 in the link you posted). Right now your ranges are so crinkly that its hard to get a read on how the valleys actually work because there aren't enough branch lines to show what's happening. But the layout is good! Keep on working! (And welcome to the Guild. Yes, spammers are an ongoing issue, but we mods try to approve posts as quickly as we can.)