Splitting required inputs into onboarding & further steps

This is my first question here so it`s nice to meet you !

I am working on a bigger desktop web application that handles events & I am having a difficult time trying to establish a wizard as I don`t know when to stop the wizard and carry on with other steps requested from the user.

So as you enter the app you can do the following steps:

-Enter event details ( name , location , image , event parts , tickets etc. ) These are basically inputs or yes or no questions. These inputs are quite a few ( 15 inputs or questions ).

-Create event parts ( start hours, gate , location if it differs from the primary etc. )

-Create/Customize event pages ( like speakers at a conference , buy tickets etc. )

-Create/Customize newsletters

and more ...

My issue is that all the steps above are connected to each other so for the user to really start using the app for it`s purpose he has to do quite a lot of things. ( You cannot create pages until all event info are filled, you cannot create email unless you have created the pages first etc. )

So I was thinking to have the "Enter event details" created as a wizard and then take the user to a dashboard where he sees the next steps that he has to take but as I still need to guide the user I`m not sure that this is the best approach. Yet making a huge wizard at the beginning is still not great as the user might not have all the info needed to finish the wizard. But letting the user roam around the app will confuse him as he cannot do steps in different order...

How should I handle this ?

TL:DR Webapp needs a lot of info and has a lot of configuration options and some configurations depends on others and don`t know how to approach this. Either by a big wizard or by steps ...