|As others have pointed out, that is a bad table schema. If you insist on having separate tables for purchase and payment then it should look like this:
AmountPersonally I would have single transaction table with a transaction type column but each to their own.
Whether you follow my advice or not, you will need to JOIN the tables based on the column that is common to all of them
Name_Provider if you leave things as they are. Here is an article that tells you how to do that Joining Tables in SQL[^]
Note we are referring to "SQL" in the sense of T-SQL - the "language" and not SQL Server the database. As you are connecting from VB.NET to Access I presume you are using ADO or OLEDB - both of which will require SQL statements.
Once you have worked out how to join your tables you already have the SELECT clause essentially written...
SELECT Provider.Name_Provider. Sum(purchase.Amount), sum(Payment.Amount)
Give it a go, but if you still get stuck reply to this message with the code that isn't working and we will try to help.