Jesus uses two questions to introduce what he is about to teach. AT: "I will tell you what the kingdom of God is like ... what I can compare it to" (See: [[rc://en/ta/man/translate/figs-rquestion]])
This is basically the same as the previous question. Some languages can use both questions, and some would use only one. (See: [[rc://en/ta/man/translate/figs-parallelism]])
Mustard seeds are very small seeds that grow into large plants. If these are not known, it can be translated with the name of another seed like it or simply as "a small seed" (See: [[rc://en/ta/man/translate/translate-unknown]])
"planted in his garden." People planted some kinds of seeds by throwing them so that they scattered in the garden. (See: [[rc://en/ta/man/translate/figs-explicit]])
The word "big" is an exaggeration that contrasts the tree with the tiny seed. AT: "a very large shrub" (See: [[rc://en/ta/man/translate/figs-hyperbole]])