thanks @Niyas Raphy
client is using Odoo CRM which model/table is crm.lead, here is a field user_id
for manager we have to approach to model hr.employee where is parent_id for Manager
now the
1) logged-in user should be the same crm.lead.user_id
OR
2) logged-in user = hr.employee.parent_id AND crm.lead.user_id = hr.employee.id

hope that clear the requirement.
regards

yes, now you can try to map the general one into your requirement, cheers

but how? this is what actually i want to know. please help.

dear Jaideep, first, thank you to at least trying to help, 2nd please read thoroughly what WE already have posted here and 3rd we all are working in developer mode when customizing any new or existed module(s).