They are very similar. I would say that "under" refers to objects a lot. For example: The ball is under the table. I found the cat under my car. "below" is a bit more abstract. For example: The price of the house is below market value. The temperature outside is below freezing. My test score was below average. This could help... https://www.englishgrammar.org/beneath/ Dont worry too much because a native or fluent person will 100% understand you and these words are very very similar.

The kite is bellow to you..and my cat sleep under my bed.