pass data between 2 dropdown forms

I have one MySQL database which has a data base with soccer games, teams, leagues, date, time, and some other things. Here is an example of a record.

Arsenal - Crystal Palace - ENG PR - 2018-01-20 - 19:30:00

I also have one php file which has 2 forms (form1 and form2). Both forms are dropdown menu Form1 give the choise to user to select one league from different Leagues (for example ENG PR-IT 1-FR 1-GE BUND-GE 2-etc) I want, when user make a choice in form1 for example FR1 then in the dropdown form2 appear the games from the database which are in FR1 league only and the user make a choice from that games only

I make the first form (form1) and i retrieve data from my database but i dont know how pass the result in the fields of form2 Any idea please? I have installed Apache2.4 - Php 5.6 - and MySQL 5.7 All works fine I have little experience with php. I have read in internet (and here) that in some cases this is possible with java script and also that is possible with little code in php But i have not found some clearly examples to do that with Dropdown menu

You may see something that, in work in the page http://www.bettinginf.com There the user make a choice to which sport want, and automatic the other form fill with games from this sport Thank you