1. What is one problem with the substitution cipher?
One problem with this particular cipher is that it is reeeaaaasonably easy to break using ‘frequency analysis.’ By calculating how many times a certain letter occurs, referencing the frequency of understandable letters allows the decipherer(?) to assume which letters/numbers/symbols correspond to which letters.
2. How can this problem be overcome?
One way to overcome this obstacle is to substitute spaces with a combination of letters (a combination is necessary as a single letter may be confused with another letter. Another method is to place certain symbols after certain letters are written (eg. after every letter ‘A’, you can place an the letters ‘EN’. I received this idea from the beloved series Deltora Quest).