my contact form needs to be fixed

Hi there, I have built a website and i'm happy with it, NO CHANGES required please. This is a HTML built site. What I need help with is the contact form...right now it works fine but i noticed i'm getting some blankspam emails coming to this address since my site went live. it will send me random blank emails and i'm not sure whats causing this but its giving me a headache..i'm sure its a small piece of code i'm [login to view URL] i need some type of verification? Also i need a message that should appear after a user successfully submits a query -it should say "Thank you for contacting us, we will be in touch soon...") I need this to be fixed and tested very carefully please as I plan to deploy this soon, i also need good open and honest clear communication please, if you're not sure about anything ,pls ask me. also payment and review AFTER the work is completed 100% satisfactorily please, do not ask me before. If you read and understand the above and are comfortable please contact me. I look forward to working with you Thank you