Bottleneck for my gpu?

Performance isn't a one size fits all for all os all scenarios all vendors.   Several Factors are applicable.

If you have 32 bit OS you should have At Least 3.5 gigs of ram.   If you have more than 4 reinstalling with a 64 bit os will improve performance.   Adding Ram up to 8 gigs will also improve performance but none of the MHz myth or Somes good mores better proportionality applies.  2X ram is not 2X faster nor is 4Ghz single core better than 1.8Ghz Dual core.   Netburst Single or Dual Core is SLOWER than Core2 Duo at the the same and even higher clock speeds.  So a 3.8Ghz Pentium 4 is not as fast as a 1.8 Ghz core2 duo.

If you need more performance add ram,  Add a Geforce 750TI GPU (If your machine will take 2 Slot wide card.,  Add a Core2 duo in the 2.4Ghz or faster range.  If you cant take a dual slot card upgrade to a Radeon R7 250E.  Sapphire 11215-06-20G Radeon R7 250 1GB GDDR5

Visiontek 900695 Radeon R7 250 1GB GDDR5

http://www.newegg.com/Product/Product.aspx?Item=N82E16814129294

I have an Optiplex 620 with 3.6Ghz Pentium D and 3.5 gigs of ram with a Radeon R7 250E aka HD7750 running windows 8.1 64 bit and it works Just fine.   Windows Experience Index is locked at 5.9 because It does not have an SSD.   If it had an SSD the WEI would go up to 6.7

I totally agree with you but...... i play for example League of legends ok?

I saw that my GPU can run that game maxed out with ~100 fps.With my specs i can't play on max because ill get under 30 fps + my cpu is 100% used,and if i' m speaking with someone on skype too...im lagging sometimes on medium settings due to processor which is overused.I have 6 gb of ram DDR2 with win 7 64 bits, when i play that game i have only 2.23 gbs of ram used so i dont think that is the problem.

With my old graphics card i ran same game on low settings my cpu usage was like 20-25% ....it's ridiculous, and with the gt730 my cpu is at 60-70% .

That's why i suspect my processor can be the problem

I can run CS GO at 40 fps on lowest and my gpu is more than enough to play that game on max.With an i3 you can max that and get 60-100 fps easily.

And besides all these things my temp on that card is like 35 C stable when i play with fans at 40% so it's something that it doesn' t let my GPU even "breathe".

That bottleneck comes from somewhere and i see the CPU doing that in the most part .In some cases i reach like 60 more fps and then comes a big drop.

All the best bud!

And i have a 128 GB Intel SSD besides all that

The bottleneck is a non gaming el cheapo GPU.

All gpu's these days steal up to 2 gigs of system ram with Hyperjunk on AMD to TurboTrash on NVIDIA.

The GTX 750 TI is a 128 Bit GPU and the GT 730 is a 64 bit GPU.It is at LEAST 400 percent Slower than the 750 TI.

The GT730 64 Bit

3DMark GPU Score:1800

Shading units     384
Texture mapping units     16
Render output processors 8
SMX units     2

The GTX 750 TI 128 Bit

3DMark GPU Score:5630

Shading units     640
Texture mapping units     40  
Render output processors     16
SMX units     5