Blockquote but I do terrible in weightlifting. I have no experience in weightlifting at all.

This is the reason you 'struggle', weightlifting is very much a specific 'skill'. It takes years of practise. If you were to take one of your crossfit class members snowboarding for the first time i'd imagine they'd feel pretty terrible next to you. Cardio and weightlifting build up the muscles differently. So being strong and having good cardio is a completely different type of muscle. As others have advised i would get some coaching.

Just as a side note the snatch is a diffcult movement. It's very technical(in comparison to something like a squat) and requires a good deal of co-ordination. whether you can do the bar or not any good weightlifting coach wouldn't let a beginner progress much past the bar until they had the movement down to a reasonable standard. I would wager most people start with the bar, whether they are strong or not because of the technical nature of the snatch. For example, i bet you could press the bar overhead without too much issue and i'd also bet that you can squat the bar without too much issue. So it's not really that you're weak, it's more that you dont know how to do the movement and you haven't practiced enough to gain the muscle memory. Also after having been around weightlifters i'd say that 99% of coaches prefer a weaker beginner to someone that's already strong Because a weaker lifters has to focus on technique more and it's easier to build strength than good technique.

If you wanted some more information there's plenty of good weightlifting channels on YT. I would recommend Zack telander, Max Aita(juggernaut strength) for informative content that does'nt really require any prior weightlifting knowledge. There are some good videos out there that feature dmitry klokov, Oleksiy Torokhtiy or Gabriel Sincraian who are all olympians. However the latter 3 might require some basic knowledge of some weightlifting Jargon.

but I do terrible in weightlifting. I have no experience in weightlifting at all.

This is the reason you 'struggle', weightlifting is very much a specific 'skill'. It takes years of practise. If you were to take one of your CrossFit class members snowboarding for the first time I imagine they'd feel pretty terrible next to you. Cardio and weightlifting build up the muscles differently. So being strong and having good cardio is a completely different type of muscle. As others have advised, I would get some coaching.

Just as a side note the snatch is a difficult movement. It's very technical  (in comparison to something like a squat) and requires a good deal of co-ordination.

Whether you can do the bar or not any good weightlifting coach wouldn't let a beginner progress much past the bar until they had the movement down to a reasonable standard. 

I would wager most people start with the bar, whether they are strong or not because of the technical nature of the snatch. For example, I bet you could press the bar overhead without too much issue and I'd also bet that you can squat the bar without too much issue. So it's not really that you're weak, it's more that you don't know how to do the movement and you haven't practiced enough to gain the muscle memory. Also after having been around weightlifters I'd say that 99% of coaches prefer a weak beginner to someone that's already strong because a weak lifter has to focus on technique more and it's easier to build strength than good technique.

If you wanted some more information there's plenty of good weightlifting channels on YouTube. I would recommend Zack Telander, Max Aita  (juggernaut strength) for informative content that doesn't really require any prior weightlifting knowledge. There are some good videos out there that feature Dmitry Klokov, Oleksiy Torokhtiy or Gabriel Sincraian who are all Olympians. However the latter 3 might require some basic knowledge of some weightlifting jargon.