السلام عليكم ورحمة الله If you’re in the same area where your home is but you’re selling food and you can’t close cuz it’s not a shop, also it’s full of crowd and it’s maghrib time can you conjoin it with isha ? Or is it a must you pray on time ?

Being busy at your selling spot, even when it is crowded, is not a valid reason to combine Maghrib with ʿIshāʾ, so you pray Maghrib in its own time and then pray ʿIshāʾ in its time. The excuses the scholars recognize for combining are matters like travel, illness, and rain, not being occupied with work or fearing the loss of customers, especially when your spot is near your home and you can step aside and pray Maghrib quickly, even in a couple of minutes, then return. Combining is only for a genuine pressing hardship that truly prevents praying on time, and it is never a standing habit.