Is there anything grammatically wrong or inappropriate？ Certificate

This is to certify that Mr. Lee, male, student No:2015955, was born on May 4th, 1996, having passed National College Entrance Examination, was enrolled in Economics School of China Ocean University in Sepetember, 2014, majoring in International Economics and Trade. The length of schooling is four years. Now he is a Senior.

Academic Divison of China Ocean University

why is it "where" in this sentence？ There is a line：Sometimes you have one of those days where you are surrounded by people but you still feel pretty lonely

Question：

Shouldn't we use "when" in this sentence instead of "where"？

A problem with punctuation Technological innovations in agriculture have increased yield of farmland and use of machines and industrial robots has enable factories to produce products faster and at a lower cost.

Is there any punctuation problem in the sentence above？

Dose the word "lemming" mean… In the UK, dose the word "lemming" mean that people follow an action without thinking about it？

Is "tacky" a saying in Britain and America?

Is there any wrong grammatically? I had been try to lose weight by running for about thirty minutes every day. But I just found it's not easy to stick with. Because if after many days' workout I found that i didn't lose my weight at all, which literally could psych me out of workout, i would bow out then. I mean, I couldn't roll over any faster at that time.

A question about would have You're handling this matter better than i would have expected. You're handling this matter better than i have expected. What's the different meaning of this two expression?

about there is What does 'there is' mean in the follow sentence? I think I've got one of the most stressful jobs there is.

about'the' The increase in people’s weight can be explained by the following reasons. In this sentence, why should we use 'the' in there？