I did plug it in the electrical converter and it is how it work.Ok, in your third video, the green pump that you started with is a 220V pump. It needs to be powered by 220V in order to run properly. It will run for some time on 120V but not properly and it will kill the motor early. You are most certainly seeing it under-perform, which is probably why it seems so weak.
If you can't find a way to power it with 220V then it is, unfortunately, no good to you.
If you look at the Pondmaster pump that I posted then I think it could possibly be a solution for you.
As i said in the video, bought the lp100 in Indo, so couldn't returnOh ok, I would return that one, if you can.
I think the best advice I can offer at this point would be to try out the Pondmaster pump I posted a link to or to just stick with your original pump (the silver one) and buy four or five more of them to run a multiple pump setup.