I graduated from tourism management and want to switch to mechanical design. Is it okay?

Yes, but it's hard! You should first check the basic knowledge of mechanical design specialty, and then work hard in the direction you want to develop in combination with your personal hobbies, but you must be mentally prepared! Maybe you actually use only one point of mechanical major, but you often have relevant knowledge to dabble in. However, you can position your development direction in the non-professional field of this industry, which may make it easier to enter!