Same supplier is customer ( how to link accounts )

Hi supportive people
i do have supplier and at the same time he is customer
how i can link client and customer account
so the amount will be automatic adjusted what he give me and what i give him

thanks in advanced

You actually cannot link them. However you can make compensations between customer and supplier through journal entries.

Keep in mind that by law you cannot make an automatic compensation between debits and credits without a written contract with the counterpart listing the invoices and with the exact amounts to be compensated.

Read this Guide Offset simultaneous sales and purchase invoices | Manager
Nothing in Manager automatically happens.
Depending on where you are in the world, a written contract may not be required - just a commercial arrangement (agreement) between the parties.