Hi deborazb,
I don’t know Portuguese so that will require you or someone that can translate the plugin into it.
The plugin is translate ready, so all you will need is piece of software installed on your computer called “PoEdit” . When that is installed you will then open up the plugin folder for WP Modal Login and open the “geissinger-wpml.pot” file found in the lang folder.
This will then allow you to translate all the text the plugin contains. You can then email it to me (cole (at) colegeissinger.com) and I’ll include it into the plugin.
Here’s more info from WP on how this is done. https://codex.www.ads-software.com/Translating_WordPress#Translating_With_Poedit