Hello
1. To increase or decrease the sold out label font size you can use the below CSS code in Theme Settings >> Custom CSS >> Global Custom CSS:
.product-label.out-of-stock {
font-size: 25px;
}
2. To edit the “Search Category” there is no such option but you can translate this word by using Loco Translate plugin.
Screenshot: https://jmp.sh/Bv6tYeT
You can check the video tutorials to use the Loco Translate: https://youtu.be/D3NsDdMzsls
3. You need to make sure that you are selecting the correct html block for your 4th item in the categories menu. As it is shown as a simple WordPress menu not a mega menu .So must select the correct html block from Appearance >> Menu.
Screenshot: https://jmp.sh/hq0U8sE
For the size of menu make sure that you are not using your custom CSS. If you have any just undo it.
Best Regards.
.
