Garfish And Shrimp Mates Help

So i recently setup a new tank with a gar(i dont know what species it is so dont ask me).I put it in a tank and i thought it was too small,it has to bend its back quite frequently to turn so i transferred it into a new and bigger tank.But, the downside is that tank is already filled with shrimps about 3cm long and they seem to grow pretty fast(caught them from a pond near a waterfall) and they were a little bit aggressive as in (went into self defense mode when my gar got too close) and they would steal the feeder minnows i gave to the gar(they taken the minnows b4 my gar could get to them) so the question is will there be any effect on my gar?it keeps staying on the water surface when the shrimps are at the bottom...HELP

Another question,the current in my tank seems a little strong and keep blowing the plants around the tank (the filter is those which are kinda like a waterfall) the thing is my gar stayed away from the part where water is flowing into the tank.
So i need help!!THX

Almost forgot my gar is about 9-10cm

Its really hard to help with the gar when we dont know which type it is . From memory a lot of gars do tend to hang around the surface and are primarily an ambush predator ready to snap at smaller prey as it swims by.
By the sounds of it you may have a macrobrachium species of shrimp, or a yabby/ crayfish all of which will snatch and eat fish.

Can you post some pictures of your gar and the shrimp, we maybe able to help you identify them. Also which country you are in will help narrow down what shrimp are wild in your area.

thx for the reply baccus,heres the photos of one of my shrimps(its just a small 1 cant take pictures of the bigger ones cuz they are all hiding in the grass) and my gar

my gar