Is 'happen' the same sign as 'occur'?
Yes, the sign for 'happen' is also used for words like 'occur', 'event', and 'incident'. The context of your sentence will make it clear which English word translates best.
Do I need to mouth the word 'happens'?
You can mouth the word 'happen' slightly to clarify your meaning, especially if the context is ambiguous, but executing the manual sign clearly is the most important part.
Can I sign this with just one hand?
No, 'happens' is a two-handed sign. Using both hands is necessary to convey the correct meaning and maintain clarity, as many ASL signs rely on symmetry.