How do I get rid of the skateboard ramp?

Just go into your inventory, and when you are in the aerial view, click on the item you want to remove. When the options come up, click on the inventory symbol, the suitcase, and it will go into your inventory, ready to be put out again later if you choose. Or instead of taking it into inventory once you have clicked it to select it you can drag it to a new location on the plot.

My suggestion is to buy a empty lot and had stuff like a BBQ and a trampoline and a pool and some chairs
Also a smaill room for bathroom sink and refrigerator

I want to sell my Skate ramp (that's comes with the skaters pro house) because I don't need it and I need more money

Heres my tip: If you only have a normal sized house, then save up for another pro skaters dream pad on the ocean view estate. These Houses are much bigger.
Also, I don't know if this works, but you could try demolishing the house so the Skate ramp goes into your inventory, then sell it and rebuild the house. Other than those, I don't know...

I can it sold for 735,000 simolons