Hello,
1. Slider height I on full HD is as per in slider setting https://prnt.sc/oomx16 the width is limited by the width set the Theme Settings.
2. I have deactivated the plugins and the search works https://prnt.sc/oomz8i
3. Please add this code to the Theme Settings > Custom CSS > Global:
body .single-product-page > div{
padding:0;
}
4. Most likely, your website performance suffers from the content you have added to your website. It may happen in case of too many plugins, large not optimized images or other resources. So we suggest you to remove unnecessary plugins, install some kind of JS & CSS optimizing plugins like Better WordPress Minify and a caching plugin like WP Super Cache. Also, you can use GTmetrix tool to see what makes your website slow and optimize these parts of your website
Best Regards
.
