Doc does boiling mixed beans in water n having them. ....With an aim to achieve protein? Does it gives protein or its nutritional value decreases?

Beans and protein. Beans are valuable sources of protein, especially for people who eat vegetarian diets. Soaking dried beans in water before cooking them helps remove indigestible sugars that lead to flatulence -- it won't change the protein content.
Raw ; Digestion. Raw vegs retain the most nutrition but can be difficult to digest. You can consider par-boiling the beans so that much of the nutrition is retained as long as you are able to digest and enjoy them.