Drop down menu with preset values and the option to chose "other" and type your own value

Hello everyone,

As the title says I am looking for a tutorial on how to create a drop down menu with preset values and also the option to choose other and type your own value. I’ve found a few outdated tutorials on just creating a drop down menu but they don’t seem to cover everything I am looking for.

I will be taking these answers and saving them to a firebase db so users can see their reminders every time they open the app.