I Buy And Sell To Same Party, How To Manage That In Book Keeper App | Can Same Account Be In Customer Supplier Both | How To Purchase And Sell To Same Party

First and Simple option is to create two separate account. One in Customer and One is Supplier.

You can keep their account name different like:
Sanjay-Customer

Sanjay-Supplier

But in Display Name, keep it as Sanjay only.

and you can normally make all the vouchers and While viewing report, you need to check two Ledger reports and then manually check and adjust balance.

Another option is:

1. Findout, do you purchase more from this party and sell less items?
    or in simple terms, if you make more purchase vouchers for this party and less invoices
    Then create his account under Sundry Creditor/Supplier

    Now you can create normal Purchase vouchers and Payment To Suppliers
    and while selling, you can create normal Sales Voucher
    But when he makes you payment, you have to create Income voucher rather than Receipt From Customer. You won't be able to set off invoices. That's the only change.
   You will be able to view combined Ledger report. No manual work, No manual adjustment.

2. If you sell more items to this party and purchase less
    Then create his account under Sundry Debtor/Customer
 

    Now you can create normal Invoices and Receipt From Customer
    and while purchasing, you can create normal Purchase Voucher
    But when you make payment, you need to create Expense Voucher rather than Payment To Supplier. You won't be able to set off Purchases. That's only change.
   You will be able to view combined Ledger report. No manual work, No manual adjustment.