Popups With One (Single) Upsell Product
For popups with only one upsell product, you can just create a NEW custom template and write your own text in your language. You can do so by going to the menu in your admin area: Popup Templates > Add New. You can create as many popup templates as you want. See screenshot below:

Popups With Multiple Upsell Products
For popups with more than one upsell product (multiple upsell products), you can translate the strings found on the pre-existing templates by changing them from the option page. Go to Woocommerce > Upsell Popup > PRO. Please refer to the screenshot below:

Translating Strings By Creating Custom Template
Another way to translate the strings on popups with multiple upsell products is to duplicate an existing popup template and change the strings from the PHP file. The full tutorial on how to do so can be found on this documentation page (click here).
Other Ways To Translate Popup Strings
There are other ways to translate the strings on your popups. One method is to use programs like Poedit.
First, download a program called Poedit (it’s free) and install it on your computer. Then for our plugin, you go to the “languages
” folder inside the main folder, the path looks like so:
/wp-content/plugins/very-simple-woocommerce-upsell-popup/languages/
Inside this folder you will find a file named very-simple-woocommerce-upsell-popup.pot
. Download and open this file with Poedit on your computer. Once it is open, you will see a button on Poedit (at the very bottom) that says “Create new translation”. Once you click this button, you will be shown a new window where you can add translations to all the strings in our plugin.
Save this new file in .po
format and upload to it to the same folder as above. Make sure your WordPress site is set to use the same language as the one you translated to above.
Using WordPress API Gettext Hook
Another way to do translation is to use WordPress API gettext
hook. Here is a code snippet showing how it can be done:
You can copy and paste the code above into your theme’s or child theme’s functions.php
file, edit the text to translate and translation text as needed.