If you want to progress quickly in Brazilian Jiu Jitsu, then you will need to take charge of your learning at some point. As a white belt, your best bet is to just get as much time on the mats as you can. There’s not much point in supplemental training because your problem is not a lack of cardio or strength (no matter how much it feels like it), it’s a matter of lack of knowledge, and lack of muscle memory to perform the basic motions of the sport.
You might be lucky and have an instructor that has the same body type as you and a similar game, but if not, your options are learning from others in the gym, watching bjj instructional videos and learning from seminars and open mats.
White belts will do better focusing on what their instructor is teaching them, and drilling the basics. It’s not really ideal for a white belt to watch instructional videos – especially not free ones on YouTube, because they are not going to be able to tell which ones offer good advice and which ones show poor technique. In addition, there’s no point drilling berimbolo, worm guard, or single-leg X if you don’t know how to escape mount or how to frame properly when someone is passing your guard.
Eventually, however, you will need to start to take charge of your own learning. For most people, blue belt level is the time that you become a ‘technique collector’. It’s when you learn a lot of different passes, a lot of sweeps, and submissions from each position. Then, as a purple belt you’ll look to consolidate that, find some go-to moves and ways to set them up so that you are able to confidently control and submit people with your favorite moves.
Ideally, you would find someone who has a game that you like, and then watch their videos, take notes, and drill the moves at open mat.? Most high level competitors have their own subscription sites now, with videos categorized by type, position, etc. If there’s a competitor that you like a lot, then subscribing to their service and watching their videos makes a lot of sense.
Put the videos on your phone and take them to open mat with you, and then drill the moves with a partner (ideally someone close to or better than you in skill level so that you can dissect the move together). You might need to pause and replay the move a few times to truly figure it out. That’s why it’s so important to have the video on hand while you drill. If you can, don’t just watch that one video on the move – watch other videos from other instructors and compare the way they do things. Sometimes, a simple thing such as a change in grip can make a big difference to how a move feels for you – there’s no one single ‘right way’ to do jiu jitsu.