Dear sir, according to the photograph, it looks like normal tartar that formals on teeth regularly despite of brushing.
The plaque on the teeth hardened due to
calcium ions from the saliva and gets deposited on teeth time to time. This has to be removed by a procedure known as scaling by a dentist
Next Steps
Do not worry and get disappointed, it is normal for tartar to form. Some people have a faster tartar formation, some have slower.
Health Tips
That is why dentists recommend scaling and polishing of teeth once a year .