User restriction under come company

As our work model structure is individual trading under single company, we need to have restrictions as follows….

1- Users not to access other users quotations, purchase orders

2- Accounts user can have access to all users sales orders & invoices

3- Administrator can have complete access to all users data (quotations, POs, SOs, Invoices, etc.)

This will help answer your questions https://erpnext.org/docs/user/manual/en/setting-up/users-and-permissions