You dont need to paste your solution here because we know it is not right, and we know what is wrong with it. Run your solution in your PyCharm twice, like this:

print(is_pangram(" bcdefghijklmnopqrstuvwxyz"))
print(is_pangram("abcdefghijklmnopqrstuvwxy "))

and see what is the result. (edit: fixed the example)

Yes, because you only run one test at once. Try running a test which expects True and directly afterwards (next code line) a test which expects False.

Your solution will not work when run twice in a row.

is your code failing all the tests?