What to use for the SITE+MOB project. Appendix?

Question

CMS

Please do not kick and treat with understanding.
Please tell me which platform to choose and with the help of which languages, frameworks and technologies it is best to implement such a project. And also what specialists to involve:
There is an idea to make a website + application. For the site I think to use bitrix. I don't know about the app.
Website: something like social. a network in which the supplier and the visitor have personal accounts. The supplier through his personal account can add an ad marked with a geo position, and the client, in turn, can filter the ads that are next to him and place an order. (something similar to youla.io) The main condition is to display these ads on the map within a certain radius. (you can google or yandex api).
Mob. application (android, ios): reflects ads that are added through the site. These announcements can be reflected both in the list and on the map in the form of marked points (by clicking on the point, you can go to the announcement). The main condition is that points are reflected located within a certain radius that can be narrowed and expanded (let's say 5km-30km).
Also, the application needs a chat function that also works within the specified radius and reflects messages (sends messages) only to those users who have this application and they are in this radius.
User LC. In the personal account, you can view purchase statistics, add to favorites, view product ratings, view your comments on products.
Supplier's LC. When paying for one of the packages, the supplier is allowed to place a certain number of goods. At the end of the month, automatic renewal when replenishing the balance. The supplier in the personal account can add products, view their rating, reviews on them, manage incoming orders. Also, for each supplier, the user can look at the summary statistics (overall rating).

Answer 1

Ну про кмс можно забыть. Для backend взять Golang (или другой ЯП но я бы взял его), а для клиента javascript (cordova для мобильных)

Answer 2

Если нет большой разницы для бэка, юзай Django+Angular+Ionic)) А про битрикс правильно ответили)