Hi Sumistha,
For a 2nd year BA student I will say you are very good at sketching. The way to get good at this is to keep doing more of them, repeating and improving every time. Your colored pencil sketches are very good, keep working on the details. It is when the eye focuses and the sketch still looks realistic it becomes a very powerful sketch. Because the eye has a fairly small area of focus, adding only a few very sharp details, highlights, material indications, will make the sketch look more realistic. I can’t tell that there is metal in the sketch, if it is a black chrome or piano black high-gloss plastic. I have no experience drawing black chrome but because it will absorb less of the color relative to black paint I imagine that it will work to add a hint of a cold color in parts where it will reflect the sky (say a Pantone 7672) and a warm color like a light mars red or sand color for the ground reflections. The line drawings in your third post are very expressive, and because of the perspective the shapes are well readable. A lot of your other sketches appear quite flat. Keep posting!