Is there a problem if the systolic number of a blood pressure is bellow 80 but the dystolic is just normal?

??? Systolic is the first/top number and is the higher. It's the pressure your heart generates when squeezing. Diastolic is the lower one from when the heart relaxes. A systolic below 80 would usually make an adult pretty dizzy. Diastolic would be low also, so i think you may be reversed. Check again in both arms.
Yes. I am not sure what "normal" diastolic blood pressure to you is. If it is 60 and higher and your diastolic is below 80, that means that your heart manages to pump out less than 20 cc with a stroke. That's a problem. I am afraid that you BP cuff is either not working properly, or you have a significant difference between the arms or indeed you may be having a problem with your heart and/or arteries.