How to split leagues? top # moves to 'champions group, bottom to 'loser group'

[Jaapschap]

I've never done a split league before. So i'm looking for some advice how to approach this.

The idea is that i have 8 groups of 10 teams. They play each other twice.

After these games the top five from group A goes to a new group to play against the top five from group B.

Once again, the teams play each other twice.

After that, the 4 'champions' group winners need to play each other in a cup play-off to determine one almighty champion.

While in the 'loser group' the bottom 2 teams (so 8 in total) will relegate.

I have no clue how to even start here.

Do i need to make it 1 parent competition or are the 3 stages (overall, champions, losers) all separate?

Thanks in advance.