The real answer is "However long it takes." Why worry? You are going to keep at it until you can do it, and then will keep doing it thereafter ... so now that you have already started, it will take however long.
None of us here know you, so none of us can gauge how fit you are, what you eat, whether or how much you stretch, what other activities you engage in .... none of us (nor you yourself) know how hard you will push, how much yo will enjoy the process, how quickly you will change ...
Everyone's body and mind are different.
I hope that you like cycling, since you plan to do it daily. Most posters here do like cycling and many even find it to be an important component in a happy, healthy life. if you find you like cycling you could further find that it becomes one of the joys of your life ... or it could just be a pleasant way to commute short distances, or something to do on bored evenings or weekends .... whatever suits you.
Just go do it. Don't worry about average speed or comparing your performance to others' .... you can do that later if you like, but for now, just ride the bike and see what it's like.