Meena, couple of points.
When you said it sounded like the shutter was sticking I suspect it was just a long shutter speed.
And when you said in shutter priority the pictures were blank I suspect there wasn't enough light available for the given aperture and ISO settings selected. I would also guess that the aperture value was flashing in the viewfinder when you half pressed the shutter.
Going back to basics.
Photography is all about light and there are 3 things that affect the amount of light that is available for any given shot.
The shutter speed. The more light there is the faster this will need to be.
The aperture. This is an opening inside the lens that controls how much light can pass through. A lower number such as f/2.8 means more light.
The ISO setting which controls how sensitive the camera is to the light it "sees" when the shot is taken.
When you use green box mode the camera will make all the decisions for you but when you switch to Aperture or Shutter mode you get a lot more control over what's happening. To start you on the road to learning how the controls work try this simple experiment.
Set the camera to Aperture mode and then change the aperture so it's at the smallest number, maybe f/1.8 with your 50mm lens. Next change the ISO setting to the lowest value, probably 100.
Now point the camera at darkest part of the room, a corner behind a chair maybe and take a note of the shutter speed. Now point the camera at the light source - the light or the window if it's daytime. Again note the shutter speed. Now there should have been a big difference between the shutter speeds, the first one would have been quite low and the second a lot faster.
Now change the ISO setting to the highest value you can which is probably 1600 and repeat the two experiments. This time you should find that there is still a big difference between the two readings but in both cases it will also be much higher than when the ISO was at 100.
This shows how you can adjust the ISO to increase the shutter speed being used which is important because you need to get a fast enough shutter speed to stop the blurry effects you have described. With your 50mm lens you need a shutter speed of at least 1/50s to prevent your own movement affecting the result and you may need a higher value still if the subject you are shooting is also moving.
At this point I would suggest you spend some time shooting at different ISO settings and noting the shutter speed so you can see the impact it will have on the results. From there do similar kinds of tests but instead of varying the ISO change the aperture setting or switch to Shutter mode and try different speeds to see how the aperture is changed.
Take it one step at a time and it should all start to make sense