I have a problem with my heightmap?

Hey guys, I am a new developer and I came into a large problem while trying to import my heightmap- it has some areas that are too high and some that are too low. I am trying to import the map of Europe, North Africa and The Middle East, but for some reason it looks like this- [1]: /storage/temp/58228-capture.png . At first it had a lot of spikes because I used this map- [1]: /storage/temp/58230-maphelper+form+3.png , but after some digging I found out that I should play around with the Z scaling- it only lowered the spikes but than I came across that I should add a gaussian blur- it helped A LOT. My heightmap became this one - [1]: /storage/temp/58241-maphelper+form+4.png , but even though it removed the spikes there are still a lot of issues and looks like the first image. I was wondering can you help me make only if the scale is over 0.85 to be valid otherwise it will be 0.5 and if it is below 0.2 to be like 0? These numbers are not required to be specific I just want to know if it is possible to do so. So that my character can walk on them? If you help me I will be really, really, REALLY thankful. Thank you, for reading ^^!