I expect that the green color indicates a good response time, and the red color indicates a good response time, correct? This means we have different response times depending on timing.
Yes, the red color it means that there is a downtime happen on that day, you can click or hover the red line to check what date and how many mins (only estimate) it has downtime.
And yes, since this monitoring feature only access the website in 1 minute interval so it wont know what will happen on the rest of the minute, there might some downtime or uptime that monitoring bot cannot notice. Only if the downtime is not that long (less than a minute), but if it is the otherwise, it will be monitored and recorded.
As I see it, the forum's response time is bad, exceeding 5000-10000ms, but what are the reasons that make the response time bad or long? Also, what solutions can be provided to avoid this situation and improve response time?
Longer response time doesn't mean always bad, the status green or red is based on the status code (200+, 300+, 400+, 500+) when accessing the website on the specific time.
For improvements, the faster and stronger server will always do the job especially if there are many users of the website.