Group chat splits every time someone talks?

I'm in a group chat with 17 people; I personally have iMessage, but not everyone else does in the chat. For some reason, every time someone talks, it splits into a new group chat (for me only) that only shows 10 people (out of the 17) in it. If I text back in one of these separate group chats, only those 10 people receive my texts, and sometimes my texts don't go through at all. Pretty sure I'm the only person in this chat who's having the problem. I have an iPhone 7 and my phone is up to date. Any suggestions?

Iphone have detected unusual traffic?

Earlier I did a simple Google search. I got this message Our systems have detected unusual traffic from your computer network. Its kind of freaking me out!

I don't know what has caused this to happen. Use vpn, its not a virus and there was no one else at home so no other traffic from the network. Does any have any suggestions why this is happening and is it common?

I would like to know how to backup my phone data on iTunes and how to merge data from two old phones onto a new phone

Hi, I recently purchased an iPhone SE and transferred the data from my old iPhone 4S using iTunes. My girlfriend is about to do the same, using the same computer, however she has two old phones and she d like the data merged onto her new iPhone SE.
My questions are;
How do I backup my data on iTunes? (I would like to put this on an external hard drive).
How do I save my girlfriends data on iTunes without affecting mine? Do I login in to windows with a different user account?
Finally, how do we merge the data from two old phones on to the new SE?