To express the phrase “memorize by heart” in English, you would say “memorize something by heart.” This phrase is used to describe the act of remembering something without the need for written notes or external aids. Here’s an example of how you might use it in a sentence:
“I’ve memorized the lyrics to my favorite song by heart.”
This implies that the person has committed the lyrics to memory to the extent that they can recite them without looking at a written copy.