What languages do I need to learn to create a social media/forum like app?

Question

1) can HTML and CSS be used to design UI/layout for apps as well or just websites? if not, what is used?
2) What do I need to learn to add additional features such as a Map, ability to purchase/buy, a messaging/chat option, newsfeed etc
3) I am currently learning Java, What should I learn next?
4) I know this is a "how long is a string" type of Qs, but roughly how many hours would I need to spend learning to code to build something like this? and how many hours to build it?

Thank you so much in advance😁

Answer 1

https://code.sololearn.com/WF9mD95X80Gs/?ref=app
something could be created by using web technologies and map is also embedded using Google map js api
and within a week..but with lots of bugs..
u could be perfect on a separate platform, with good usage of server side language

Answer 2

yes bro!!

Answer 3

@James, by number 2 do you mean any programming language?

@Sami Khan, what you have created is pretty neat. did you create it yourself? well done!