I wondered if the table was a drawing table with a tilted top- then the error was only the back-top width ( \ / ) rather than the top's viewed area and shelves and such, too. If so, it's a sneaky bit of sight-drawing to start with- like giving someone a foreshortened elbow-pointing at them nude figure to draw right out of the box.
One point perspective to start- lots of tutorials on that on the 'net. You will also need to learn all about dam-- dang ellipses, too- and if those don't fry your brain, you'll be off to the races.
Here's something you need to accept: In the US, especially, and likely other countries, we are not taught how to draw. We're given el cheapo construction paper, a box of crayons, for something special, some safety scissors, a pot of glue and some glitter, and that's 'Art'. Then, as you proceed through your formal education, 'Art' is left by the wayside because there's no money in it for a Regular Joe/Josephine. So you NEVER are taught the most important fundamental of Art- drawing. 'Draughtsmanship'
Which means, as an adult, when you try to 'get into Art', you spend a year or two teaching yourself to draw and are mostly unsuccessful because your teacher doesn't know the subject and your student doesn't either.
You're smart to start with drawing- the foundation of pretty much all of it. Draw every day- a shoe, a cup, a book, a cat, a box of cookies (likely empty or is if you're hungry), an apple, a doorway, the corner of your room. Try NOT to use lines other than as lightly applied way-markers; instead use blocks and shapes of shadows- passages of light and dark (if you do not get into the 'drawing = lines' issue, you don't have to unlearn it). Creative Spark has sketch exercises- might should try them.
Study other artists' drawing techniques and results, and also remember this: There's absolutely NO RULE that says you have to draw everything free-hand or it isn't 'Art'; that's just a canard- a lie. You can graph, you can use sight measuring, you can use your pencil or pen as a ruler, you can even trace or project and trace- doesn't matter. Drawing is just a foundational discipline to 'Art'.
What matters is learning to draw what you SEE- because once you get THAT, you get value, which gives you colour and composition. Which is 'Art'.