You're talking about yourself, so you should not use "us".
Honestly, I'm not too sure what you're trying to express here because I don't know what the scenario is like. But here's my take:
The desks are disorganized. Clerks should have their own desks to help customers by the terminals. Staff may sit at the computer workstations to assist customers while the rest do their duties at their desks. This way, there will be more focus and better response time in assisting customers.
In negative things, try to us we instead of I, suggest improvements and state the outcome of the improvements. The italicized text are my additions, you may remove them if you wish :)
I would request a solution that prevents the security system from going off whenever customers borrow or bring items from other departments or sections. Despite the recent installment of the new gates, the problem still occurs. It is embarrassing for them, and even more embarrassing for us to assure and to explain the technical glitch.
A collective word such as "department" or "section" is always preferred to the names of the actual departments or sections.
We could have a 3- or 4-hour loan, in addition to our current 2-hour period. As our 2-hour loans are very popular, offering that as a second option may bring more convenience to the customer and more profit in one transaction. I would like to thank you for asking the above questions.
There is no need to include "period" after "loan", because "loan" implies a period.
You should not use "a lot" after "thank you" in formal situations, even though you mean it. "A lot" is very casual and colloquial.
When companies ask for feedback, tell them things that will benefit them. That way you and your feedback is recognized.