Quick Poly decrease

how can I quickly decrease the amount of polys on my model without using the decimate modifier? or how can I smooth with it? I have tried using loop cut but it says that the loops over-lap.

When you use edge loop select, you can only delete one edge loop.
And of course you can Merge with ALT+M.
Other options are to retopo/make a new mesh.
There’s also a script, it’s installed by default.
Poly Reducer (Unsubsurf) last I tried it it was neater then the decimate modifer.

how do I usen the script?

split the window,
Change one to Scripts Window
Script>Mesh>Poly Reducer