A good question! It’s a good question because both are instruments intended for singing, and as such are considered to be the same. However, in case that’s your intention, there are differences.
In violin, a string is held above the nut, below the bridge, and above the neck to give it a flat sound; in cello it’s just below the nut, below the bridge, and above the neck. Because of this difference, it can take a little time to get used to the difference between cello and violin. In fact, violinists might feel it’s easier to tune a violin than a cello, because the strings are held a little higher in the violin (although there is a difference too). Also, since the lower strings are closer to the neck, a cello player will sometimes experience a little more neck fatigue than a violinist, especially when playing with a lot of energy.
You can also play a cello well; in fact it’s the most popular of the four main musical instruments. And one should find out how to play it before reading about violin technique on this page.
It can also be very difficult to play violin with your back to the person playing it. That is, unless you are able to see the cello or a string, which is impossible unless you hold it up at ear level.
What is the best way to learn to sing? This is a tough one, because many people simply want to find music, and this is fine, because that is, but not if they are not familiar with other types of music. Here are some suggestions:
You might want to try and find a friend to help with some of the more difficult exercises: You could even try taking some of your classical music classes online, since you may want to improve your classical singing by listening to recorded recordings of these exercises.
You could have friends or classmates at home that might be willing to help you improve on the exercises, although their understanding of music is not as good as your own, and therefore not as solid and reliable so that you can listen to them as you improve. Here is an article by Jody Burchman, who has written several books dealing with the subject of classical singing.
As well you might give it a try if you do have the means to travel to a music festival: You will get a ton of practice time from that trip, and you might also be able to take some lessons or find a class that teaches you