Help in GameMaker

Hey I'm looking for teammates for the GX jam because I'm not sure I will make it far alone and I need help, reply here or DM me on Discord @Spidey #2021 if you're interested! I need help making a 2d Runner game!! I have a really cool idea for it!
I want to have an two objects, in start event I declare health = 10;
In other script if I modify health it affects all objects??
How do I access first object and second...
GMS2 is so confusing, it seems object aren't really objects lol
Ok so 1, does the opera gx jam require a certain aspect ratio for gms2 rooms? and 2, does it require a certain framerate?
Okay so I really need somebody that is good at GML coding (Game Maker Language) to help me with my game because every tutorial is outdated or doesn't work. Please, I'm begging you. Reply here or DM me on Discord @Spidey #2021 (we can discuss percentages)
For my Opera GX Game Jam game, I'm receiving this error. Please help :(
Variable <unknown_object>.jumping(100003, -2147483648) not set before reading it.
at gml_GlobalScript_scr_jump_check (line 1) - if (jumping)
gml_GlobalScript_scr_jump_check (line 1)
Heyy guys we are new programing (like very noobs) and we are looking for someone (not necessarily profesional) who can help us!! We are two people and we speak english and spanish (spanish is our first language) if u are interesated feel free to dm me!