Optimize MATLAB/GAMS Code for Bus Fleet

I have written a MATLAB code for the optimization of a battery swapping station (BSS) for a bus fleet for scheduling its charging to minimize its cost. I have made the same code on GAMS also. This code is for a 24 hour period and for 11 buses and 4 batteries on the BSS. My code is perfectly working when I am running it for 10 hours, 2 batteries on BSS and 3 buses. But when I am increasing the number of hours or buses or batteries then it start taking a more than 3-4 days to run and still running.
I know in my problem, the number of variables and constraints are not much and GAMS has the capability to solve problems with millions of variables but why not in my case?

How can I solve this issue.

I'm seeking an expert in MATLAB and GAMS programming to optimize a code for a battery swapping station. The focus is on a bus fleet with the following parameters:

- Operation Time: More than 20 hours
- Number of Batteries: Less than 10 batteries
- Number of Buses: 10-20 buses

The optimized code should maximize the efficiency and capacity of the battery swapping station under the provided conditions. With the current parameters, the code works for 10 hours with 2 batteries and 3 buses. Your task is to expand its capacities following the new requirements.

Ideal skills and experience:
- Proficiency in MATLAB and GAMS
- Track record of code optimization
- Understanding of battery swapping stations
- Experience or interest in green technologies and bus fleets a plus.

Please submit bids with relevant samples of your past optimization projects. I look forward to forging a fruitful collaboration.