how do I tell if someone is flirting with me?

There's this person in my math that i sit with and i think they might be flirting with me idk heres my evidence ive been way overthinking.

1, i mentioned wanting to con someone into asking me out so i could go on a date to a bookstore and buy books without paying and then they said that while they didnt have money now they were gonna come into some babysitting money, not exactly offering but also taking my joke seriously? idk

2, vauge mention being my math sugur daddy (my math teacher way over complicates the lessons and they always speed run the lesson with me when we work on the worksheets)

3, (ok important to note for this i have a sister that looks alot like me that goes to our school and is in their science) they asked my sister for my last name so the could email me about somthing and my sister jokingly said that when they emialed they should tell me she said i was ugly so they sent 'Ps your sister says your ugy but it dont think so'

I KNOW I SOUND INSANE BUT LIKE ITS JUST THE VIBES IM GETTING Y'KNOW besides i also kinda wana date them but idk if thats just FOMO from all my freinds getting boyfreinds. Also i just need to know how to tell if people are flirting in genreal because im really oblivous aparently and have become parinod that im missing obvious signs