Salut Sayer, what's your language?
First, let me say to you that you have to lower your upload bandwith to 75-90% of your max upload speed. If you got 50 KB/s, you should limit upload speed to 40-45KB/s. This will faster your downloads and internet broswing.
I personnally never allow more than one upload at a time for one person to avoid abuse and I give 5KB/s to each upload slot (40/5 = 8 slots in your case).
Here is how you should configure the LW upload options (if you are using LimeWire, that is):