Build a base, then immerse
Learn the most common few hundred words and core verbs first so shows are not pure noise. Then start watching, choosing slower dramas before fast thrillers. Money Heist is thrilling but quick; Cable Girls and Who Killed Sara? are gentler entry points.
Pick the right accent and difficulty
Latin American Spanish (for example, Mexican shows like The House of Flowers) is often clearer for beginners than fast Castilian. Use graded subtitles so you can follow the story while picking up new words, and step up the difficulty as your ear adjusts.
Save and review what you hear
Watching builds comprehension; review makes it permanent. Save the words you meet and review them on a spaced schedule. Doing this consistently across a few series will take your listening comprehension a long way.