Why is an increase of assets a use of funds and a decrease a source of funds? Why is an increase in Liability and OE a source of funds and an increase a use of funds?

Why is an increase of assets a use of funds and a decrease a source of funds?

In order to acquire assets the purchase must be funded in some way, thus it is a use of funds. If you sell an asset you gain funds.

Why is an increase in Liability and OE a source of funds and an increase a use of funds?

When you borrow you have increased available funds, when you expend available funds you use funds.

These concepts are simple and require thought to see the implicationss