About GPU Mining (Please Help..)

I can see than when I am using nicehash to mine on my GPU with NBMiner(Daggerhashimoto) I can see that my GPU usage in nicehash GUI increases to 100% but in taskmanager the video memory usage is almost 0 and the other usage of GPU is high.When using other miners the video memory and copy usage in taskmanager is high.Why this happens ? Does different algorithms use different parts of GPU ?

Yes, you are right different altcoins use different algo to mine.

Can you please explain as I am new to this..

Correct, different algorithms affect the GPU differently. Ethereum, for example, is extremely memory-dependent. That's why when using MSI Afterburner, you set your core clock around -300, then push your memory clock as high as the card can stably handle, generally anywhere from +800 to +1400.

As the other poster said, each algorithm affects the GPU differently.