Google Analytics 4 exports one table per day, events_YYYYMMDD, with one row per event. Most of what you want sits in event_params, an array of key and value pairs, where the value is a record with string_value, int_value and double_value: exactly one of them is filled in.
The standard way to read one parameter is a subquery over the row's own array:
(SELECT value.string_value FROM UNNEST(event_params) WHERE key = 'page_title') AS page_title
Use int_value for numbers like ga_session_id and engagement_time_msec. A session is a user_pseudo_id together with its ga_session_id; a user is a user_pseudo_id.
event_timestamp is microseconds since 1970: TIMESTAMP_MICROS(event_timestamp) makes it a timestamp. In this lesson the exercises use the 1 June table; the next lesson queries all the days at once.