first of all
adverbUK /ˌfɜːst əv ˈɔːl/
US /ˌfɝːst əv ˈɔːl/
This means before anything else.
First of all, let's wash our hands before we eat.
OTHER MEANINGS
2. Used to introduce the most important point in a list or argument.
First of all, we need to decide where to go.
3. Used to emphasize that something is the earliest or most basic step.
First of all, you must read the instructions carefully.
4. Used to begin a series of reasons or explanations.
First of all, it's too expensive; second, we don't have time.