To those technical experts on the forum, can you please help me before I slit my throat!!

I think it may be a Windows 10 issue. I have been happy with W10 since purchasing new laptop nearly 2 years ago. However on some sites (not that many) that require I complete a sign in procedure with password or booking reference etc the laptop seems to take over and starts to download erm.....something! it appears as a message at the bottom left of the screen. I cannot get into the site that I want it just keeps trying. On clicking on the message it invites me to open the download with a choice of various programmes that include Word, Internet Explorer (which I don't use) and some others that do not appear to me as relevant. I use Chrome and generally it suits me.
One of the sites that I do have a problem with is the Virgin mobile website, if I wait long enough I do get into my account and look at my statement etc. The other site that I have HUGE problems with is, and I don't think it will come to a surprise to anyone on her, is my Cruise Personaliser on the P & O site!!

Yesterday I spent hours trying to get in and book trips for an upcoming cruise, and what a terrible time I had. Somehow or other I managed to get in after many attempts at the sign in, and many "downloads" that were driving me mad!!
I honestly don't think it is a specific P & O problem, rather there is a setting on my laptop that is taking over given certain circumstances.
Please, please can one of you really expert techs out there help me before I spill my blood?!!
Sorry to ramble on, but I am not that computer savvie, so any answers MUST be of the one syllable "we are talking to an idiot here" kind
Thank you in anticipation
Maureen