In the Elder Scrolls, there is no canon word for love. On this website, there are two versions of the Dragon language, canon and legacy(non-canon). To say 'I love you' using the canon language, there are many phrases and sayings you can use. A few of my personal favorites are 'Losei Dii Yol' - 'You are my fire' and 'Dii Lok Los Hin' - 'My skies are yours'. A non-canon translation for the word 'love' is 'lokaal'. As for how to learn the language, there are the lessons on thuum.org
https://www.thuum.org/learn/  

A Memrise course
https://www.memrise.com/course/183924/dovahzul-canon/

And some learning games, my personal favorite being "The Labyrinth"

Sikaav - https://www.thuum.org/sikaav/
Forelnaar - https://www.thuum.org/forelnaar/
The Labyrinth - https://www.thuum.org/labyrinth.php

Hope this was helpful, bro.