A question for English students out there! With some controversial advice for you!
Do you find the grammar "rules" related to "who" and "whom" rather difficult?
Simplistically, "who" is the subject of the verb. It "does" the action. And whom is the object of the verb. It "receives" the action.
1. "Paul is an English teacher WHO is also an accountant." - Subject. Paul is an account. We replaced Paul with who.
2. "Paul has clients to WHOM he gives advice." - Object. The clients receive advice.
Now - controversial point: Number 2 sounds ridiculously formal and natives almost never speak like this. Let the lawyers and royal family speak / write like this.
As a learner of English, say this: "Paul has clients WHO he gives advice TO".
See the changes?