New Here - Stage 4/ Colonectomy

Hi, I am the significant other/ caregiver of someone with stage 4 gastric cancer. The cancer was discovered after an emergency surgery to a ruptured colon that was caused by two cancerous growths. My partner has had his entire large intestine removed and has finished his first chemo treatment. I am looking for helpful suggestions on how we can manage a number of things: nausea/vomiting, diarrhea, what foods were more palatable than others, how to stay hydrated, anxiety. Also would value knowing how people did after chemo/ colonectomies -- basically, WHAT I WISH I KNEW BEFORE I STARTED CHEMO... Much appreciated.