Hi Luis! I honestly think the sentences you have are fine!
If I were going to make any changes, they’d all be small and based on my own personal preference. I don’t think any changes are really necessary—good job!
Take your original sentence for example: “I made plenty of food for my guests, but none of them liked it. I will try a different menu next time.”
I would personally say something like: “I made plenty of food for my guests, but none of them liked it—I guess I’ll try out a different menu next time and see if I get a better result.”
One other sentence for example: “After walking 20 minutes in the heat to the office, I hoped to get some water from the water cooler, but there wasn't any.”
Here, I would just get rid of the word “water” in “water cooler,” and say “cooler.” So: “After walking 20 minutes in the heat to the office, I hoped to get some water from the cooler, but there wasn't any.”
Another alternative could be: “After walking 20 minutes in the heat to the office, I hoped to grab some water from the cooler, but there wasn't any.”
Other teachers and I could go on making small changes to all of your sentences, but unless you really want to see a bunch of different variations, I don’t think any changes are necessary.