A few differences you may meet. They are minor, and you now have the know-how to identify and understand them.
In most of Spain, le and les are used for people generally, not only for to him or to her. So le veo is I see him, and lo veo is I see it. Elsewhere this is not the case.
Most of Spain uses vosotros for the informal plural you. It is not used anywhere in Latin America.
Many accents aspirate the s: /ehtá/ for está, /ehpero/ for espero.
2. vos, around the Río de la Plata Note
In about 30% of the Spanish-speaking world, used alone or mixed with tú, there is another word for informal you, and the verb endings shift slightly with it.
puedes → podés
the accent moves to the end, so no split
quieres → querés
same
Because the accent lands on the ending, the vowel no longer splits, which is exactly the rule you already know working in reverse.
3. Speak like the people you practise with Method
You can adopt any of these differences, and it is advisable to speak like the people you are practising with: the more you sound like the Spanish you hear, the more you understand.
Practising with people from several countries, you may end up with something like a pan-hispanic accent, or find yourself switching between accents depending on who you are with. Native speakers who move around do exactly the same.
4. Listening is a separate skill Method
Expect to understand less than you can say, at first. That is normal and not a sign of anything wrong.
The method is the one you have been using all along, run backwards. Instead of building sentences up, deconstruct what you hear: break it up and see what you can learn from it.
The more you do this, the more Spanish will slow down. It will slow right down and you will hear a lot more. So do not be overwhelmed at the beginning. Insist, enjoy music, watch films with subtitles, and try to match the English subtitles against what you hear.
5. What to do next Practical
The teacher's closing advice for after the course.
Get out and practise, and expose yourself to as much Spanish as possible.
After a while of practising, consider repeating the course. Being solid on so much will free up mental space to focus on whatever you are still unsure of.
Repeating it may feel like watching a good film a second time: a different experience.
There is a huge variety of literature, music and cinema from Spanish-speaking countries. Enjoying it is effectively studying, without feeling like it.
The last word of the course, and the one worth keeping.
The most important thing is not to forget to enjoy it, not to obsess over the destination but to enjoy the journey. You are already a Spanish speaker.
Language Transfer is a completely independent and unfunded project with no budget for promoting its courses. If this course reached you, it was because somebody shared it. Donating funds the time needed to build, practise and record new ones. More at languagetransfer.org.
The course closes on the new world your new language opens up: strangely the same one that was there all along.