How to get completions and signatures only when we press <c-space> and <s-tab>?

Hello, newbie to jedi-vim here, first of all thanks for developing this, it is really helpful.

When autocompletion is on it is taking sometime to load functions, and I could not able to type in meantime. And auto showing of signatures is also a bit distracting. Can you guys help me in this regard?. Thanks.