Hi,

1. Add any class in the row or column settings with this block, for example custom-font-size.

2. Use following css example to control it for the different screen resolutions:

@media (max-width: 1000px) {
.custom-font-size .title-xlarge span {
    font-size: 40px !important;
    line-height: 40px !important;
}
}
@media (max-width: 768px) {
.custom-font-size .title-xlarge span {
    font-size: 30px !important;
    line-height: 30px !important;
}
}
@media (max-width: 500px) {
.custom-font-size .title-xlarge span {
    font-size: 20px !important;
    line-height: 20px !important;
}
}