As an English speaker, what way can I easily learn Sanskrit for free online is learnSanskrit.org any good? I want to be able to read works like the Bhagavad Gita, Nyaya Sutras and other Nyaya works.
For reading scripture for free https://veducation.world/library
Generally, you can learn sanskrit as a beginner to say about 5-6 sentences in a flow with much practice. But the idea that you will be able to understand all scripture in sanskrit is false one(Most people need to read translation to understand scripture) .
The site you are choosing will help you to understand basics as beginner student.
You could also learn from sanskrit book Aṣṭādhyāyī(https://archive.org/details/wg1038) which is a grammar that describes Sanskrit[not recommended for beginners,you may read after learning basics]
Authored by Sanskrit philologist and scholar Pāṇini