Creating a marketplace for tour activities I am tying to setup a website that will sell tour activities.

People (local guides) can login in and create a profile and define 1 or multiples activities (i.e. a waking tour of Manhattan) with a description, a price and a calendar of availabilities (maybe just now a simple calendar system not linked to availabilities).

Tourists will come on the web site, choose an activity (by category, location...) and will choose a date for it and book it online.

I need to track the orders in the admin area and have it in the Profile of the person who created the activity.

I tied to do this with D7, marketplace module, calendar module and Ubercart but I have lots of difficulties to do it.

Do you have tips on which modules would be the best to do that (Ubercart / Drupal Commerce)... ?

I have also been looking to "rooms", "simple reservation" modules but it seems that they does not fit my needs.

Regarding the invoicing, payment, commission revenues tracking, I will plug the API of an external system like LemonWay.

Thanks.

Emmanuel.
As someone else suggested: take a look at the Booking and Availability Management Tools for Drupal (BAT). 

Roomify.us, the business providing the BAT framework announced that they are also providing solutions specifically for tours and activities rather than just rooms and fixed places.

The BAT system integrates with Drupal Commerce and its various payment gateways. It also takes over the Drupal logic very well with 'types', 'type bundles', 'events' and 'units'.

Once you understand how it works conceptually it should not be too difficult to modify BAT so that it can become a kind of marketplace where users can create their own units on the basis of pregiven tour types you have defined.