The code supplied above by Peter is correct. When copy-pasting, we lost indentations, and did not do it properly ourselves. The proper indentation must be used. Here is a link to a location that we found the same code, but with indents intact for the BerryGPS v3.5
TLDR: Use this code for the BMP388 temp/pressure/altimeter
Cheers, and thank you Peter for all the support.