If you had good success with the private lessons guy then maybe start with that. You would probably be best served by continuing at the normal class as well so that you are getting exposure to more than one individual when rolling (as this is important to developing a well rounded skillset). As for your complaints about energy, just keep at it and try and approach with a better mindset. Mindset is an overlooked element for a lot of people, if you have convinced yourself that you are weak/lack energy/etc that is going to manifest as those things and you will not become stronger either physically or mentally. At 28, unless you have some sort of health issue, you should be able to see regular increases in stamina and if you are struggling with energy make sure you are eating and sleeping enough.