Fix some design issues with a wordpress website

I made an image slider using Html, CSS, and JS just to avoid having lots of unused CSS and JS loaded on the website by using a plugins for that. Now this slider causes a layout shift. I need it to be solved (no need to keep the code for the slider, you can use any code as long as all the CSS and JS files are inlined to the main page without using jquery.

Also although I have mentioned the sizes explicitly for one of the images in the slider ( the first one) google says ""Image elements do not have explicit width and height"
I need that to be fixed too

I also get this error:
"ReferenceError: jQuery is not defined at <anonymous>:1:1 at https://www.googletagmanager.com/gtm.js?id=GTM-NGC****:337:414 at b (https://www.googletagmanager.com/gtm.js?id=GTM-NG***:338:329) at uc (https://www.googletagmanager.com/gtm.js?id=GTM-N****:49:146) at e (https://www.googletagmanager.com/gtm.js?id=GTM-N***:245:116) at https://www.googletagmanager.com/gtm.js?id=GTM-N***:32:130 at Array.<anonymous> (https://www.googletagmanager.com/gtm.js?id=GTM-N***:247:61) at Object.execute (https://www.googletagmanager.com/gtm.js?id=GTM-N***:246:312) at ep (https://www.googletagmanager.com/gtm.js?id=GTM-N***:248:984) at Kp (https://www.googletagmanager.com/gtm.js?id=GTM-***:252:7)"
Needs to get fixed too

I will need a clear report of the changes that you make so I can apply them when I make changes to the website in the future.