I made an encryption device for school how can I make it better? (All programmed in Visual Basic) How it works is it gets a random number from 1 to 30000 and changes the first character by it in Unicode then it uses that number to change the first character of the key then it gets a new random number and repeat so that the key is entangled in to the end result. Which is how it is decrypted by guessing the number for each of the key values till it is the same as what we know the key should look like the then the corresponding letter from the message is decrypted with the same number. Boy is it hard to explain and I am bad at writing I will link to the git hub when I do it https://github.com/VeryG00dName/Encrypter
The folks here aren't keen on performing analyses of encryption algorithms, and a load of code in git doesn't help much with that either unfortunately.

What I would say though is that you seem to have yourself a stream cipher.  Have a look at chapters 5 &amp; 6 of Handbook of Applied Cryptography.  

One of the issues will be your random numbers.  Consider that any computer can easily just try all 30,000 of them sequentially until the message makes sense. We can just do this and it's called a brute force attack.