No problem at all! The content will be delivered weekly but you might choose to do a little bit each day. You might not have time to do it in the 4 weeks, that's ok as you'll have access to it after the 4 week period ends. I guarantee access for a minimum of 6 months after signing up, however I don't put an end date on it so you'll have access to it for as long as I keep the website open. So find a solution that works for you. All that said, please be aware that the LIVE sessions are planned for certain points of the course, so you may want to try to have completed the lessons available at that point so you understand what I'm talking about and can ask questions about the content delivered to that point.
The other thing to say here though, is that you only get out what you put in. In order words you will need to spend time practising a skill to improve at it. And this particular skill is best learned if you are able to practice little and often, if you could manage 10-15 minutes a day that would be amazing and you would definitely see results quicker! If you put the time in you will develop good habits and improve your skills.
It's important to remember that this is meant to be fun! It's your hobby and should never make you feel stressed out! Go at your pace, you'll have access to the content for a minimum of 6 months after signing up.