The issue is that ACF is running to save the values in the ACF fields and then it is redirecting, probably before your other code to save other fields is running. What you need to do to create a filter/action for ACF and then run your other code for saving the other data in this action filter instead of where/when you are saving it. More than likely you could use an acf/save_post action https://www.advancedcustomfields.com/resources/acf-save_post/ and since it’s a front end form you could probably also use an acf/pre_save_post filter https://www.advancedcustomfields.com/resources/acf-save_post/, but I’d probably go with the first one in this case.
