It's always a good idea to start learning a new language from the beginning. Even if you are able to understand most of what you're reading or listening to, a new language can be challenging to speak/pronounce. In addition, you'll have different conjugations for the verbs, and different pronouns and lots of new vocabulary. If you start from lesson 1 in the Brazilian Portuguese Basics, you'll notice that while it is easier for you to understand the words, it might be a bit tricky to get the grammar. Fianlly, using the basics as a starting point will make you a more confident speaker. Give it a try and keep us posted. Boa sorte e até breve!