An entrepreneur can assign his rights under a contract. For example, sell a receivable for goods to a debt buyer - and they will sort things out with the buyer. Or transfer the lease from one of your companies to another - then the office will be occupied by a new tenant. Let's say more: rights that did not arise from the contract can also be assigned. For example, give a more savvy partner a request for a neighbor to pay for office repairs after a flood.
The law calls this thing a change of persons in an obligation. To accomplish this, a special agreement is signed. And there is a whole sea of nuances that you need to delve into.