Answer 1

Just a couple things:
First, the operator >=< does not exist. I would recommend avoiding using the while expression in your code as it would only result in a timeout exception.

For your conditionals, you would need to place the operators within quotes to make them a string (ex. if x == "*"). Additionally, you forgot to put the colon following the expression to show that the next line is apart of the block, and you also need to indent any lines within the conditional blocks.

Lastly, as Sololearn only runs on a system where you only gather input once, I would recommend you remove user_input4 as it would not be functional in this scenario.