I am bulking now for 3months + and lose my patience to gain more weight. It's progressing, but at a very slow rate. How many grams of muscle cell can our body grow in a day? Or in a week?

Are you clean bulking or dirty bulking?
Muscle growth can be on the slow side if you have never put it on before. How big is your caloric excess now? How much gains did you see in 3 months?

It's hard to track your progress using the regular weight scale. You need to get one of those scales that can measure your muscle mass and body fat levels. From there you can figure out how much your body is responding to what you're doing and do proper adjustments if they aren't desirable. Everyone's body is different.