Hi, please can someone explain how the interest works at the bank. Appreciate it may come across a bit dumb but I'm having a hard time working it out (and I have a maths brain!)

Whenever I deposit money and collect interest - the interest gained is always less than the percentage fine to withdraw the money meaning I always lose money including when I leave it awhile before withdrawing. Obviously I'm not doing it right.

Can someone give me some figures as examples so I can see where I'm going wrong? 

Thanks!

Bump!

Honestly, I have never understood the interest in the bank after 16 years and have never utilized it. So, following this xD