American Standard Water Closet I Am Having Problems Flushing An American Standard Toilet - Is It The Bowl...water Pressure...something Else?

I am having problems flushing an American Standard toilet - is it the bowl...water pressure...something else? - american standard water closet

The tank is American Standard Model # 4112th To clean the toilet, I offered to hold the handle to flush is complete. If an early release lever, the water is no longer reduced. The tank is very well filled, but slowly. Is this a problem with water pressure? It was very difficult to get a little more than a few pieces of toilet paper. Someone suggested to obtain a pressure-assisted toilets. I buy nice new bathroom, but I just wanted to make sure first that the problem is not something that can be fixed. I think the tank is screwed.