Expenses against two different types of job and P45 without tax deduction

Hello everyone I have submitted my tax return for last year, but now I have a doubt. I work as a freelance, but in 2023 I also worked for a school one day a week only, so I filed the return as an employee and I added my freelance income as well. First doubt: my P45 did not show tax deduction, so I assumed that it was a net amount. In fact, the actual amount I was paid was more than what the P45 showed and I add the difference as tax. Second doubt: the amount of expenses were not calculated against the whole income (school and freelance job) but only against the freelance job, so I don't know if I made a mistake and, if this is the case, how I can I amend it! Thanks in advance to anyone who can help!

Hi,
Please see the following link:
If you need to change your return
Thank you