Help Project - Build a JavaScript Calculator

I did the calculator project through the help of web dev simplified - i followed his steps to understand the project better, however i cannot pass the project since :

User Story #7: At any time, pressing the clear button clears the input and output values, and returns the calculator to its initialized state; 0 should be shown in the element with the id of display .

User Story #13: If 2 or more operators are entered consecutively, the operation performed should be the last operator entered (excluding the negative (-) sign). For example, if 5 + * 7 = is entered, the result should be 35 (i.e. 5 * 7); if 5 * - 5 = is entered, the result should be -25 (i.e. 5 x (-5)).

can someone review my code and help me understand how to fix the issue.

here is my codepen link: