|You are misunderstanding what Task Manager is telling you.|
Some things to understand:
1. The memory labeled as "Available" is not all free. Most of this is actually in use. In a modern OS having memory in use and available is not a contradiction. Nothing in Task Manager will show actual free memory.
2. The graphs labeled as "PF Usage" and "Page file usage history" are not actually showing pagefile usage at all. This is really the same as the commit charge but displayed in different units. The commit charge is difficult to explain but all you really need to know about it is that it should be well below the commit limit.
Actual pagefile usage will usually be well under what the graph implies. There is no way to tell actual pagefile usage in Task Manager.
Your computer is working as it was designed to work. There is nothing wrong, nothing to fix. The actual use of the pagefile is far more complex that you imagine.
I don't know why Microsoft labeled those graphs as they did. This has caused enormous confusion, even among some computer professionals.