MySQL query :

with cte as ( Select start_date,end_date from projects order by start_date asc )

,cte2 as ( Select *, end_date - row_number() over (order by start_date) as id from cte )

,cte3 as ( Select min(start_date) as start_datemin,max(end_Date) as end_datemax, max(end_Date)-min(start_date) as delay from cte2 group by id )

Select start_datemin,end_datemax from cte3 order by delay asc, start_datemin asc