ANSWER:
In Islam, it is prohibited to sell what you don’t actually possess. You are bidding over a speculation of stocks that you don’t own! This is gambling and prohibited transaction.
Some scholars say that one can buy it if the financing is less than 30%, but I couldn’t find any evidence on such an opinion! Therefore, this is not permissible.
In order for any investment into the shares of a company, two conditions must be fulfilled:
1- The line of work is halal.
2- The company doesn’t deal in Riba by financing its activities through riba or through deposits.
https://islamqa.info/en/answers/112445/ruling-on-buying-and-selling-shares
https://islamqa.info/en/answers/69941/the-difference-between-shares-and-stocks