Groups on iMessage

How do I remove a group from iMessage. I’ve moved companies and really don’t want that group.

also I have a group sign about 15 + people from a while ago how do I remove some members from there.

the instructions on YouTube don’t work. I can’t just swipe to delete. I have an iPhone XS. This is getting on my nerves now, having tried various options.

thanks for your help

kind regards