“If the chazzan is saying kedusha i think you have to stop whatever you are doing and say it too- even if you are in middle of shemona esrei (i think i once learnt that)”
Not true. One may NOT interrupt S”E to answer Kedusha, unless he or she is holding in the last paragraph (Elokai Netzor).
However, if a person recites the silent Amidah and, as he completes the Beracha of “Mechayei Ha’meitim,” he hears a congregation in a different Minyan (or even his own minyan) reciting kedusha, he should recite kedusha together with them.
“noti said you should stop SE during Kaddish, not that you should answer
just like Kedushah you must stop saying SE but you dont say anything, ive been told you should rise up on your toes at the appropriate times though”
There is no such halacha (about rising on one’s toes).
“A shliach tzibbur who says “ga’al yisrael” in an undertone. It shoud be recited out loud.”
It’s complicated.