Welcome to the community, @Tamas_Puskas!
Unlike Excel, Airtable doesn’t give us any formulas that can be used for counting/summarizing rows. The exception to this is the rollup field, but this only counts/summarizes rows of linked records from a linked table.
In your case, you will probably want to use the Summary Bar, which automatically gives you a variety of functions to use across rows. You can also group your records to get summaries of individual groups, as well.