Cant fix error code 1055, how do i solve it

Question

here is the ER-Diagram: ER diagram

I keep getting error code 1055 expression #1 : "Error Code: 1055. Expression #3 of SELECT list is not in GROUP BY clause and contains nonaggregated column '1ik013v22-grp06.religion.Namn' which is not functionally dependent on columns in GROUP BY clause; this is incompatible with sql_mode=only_full_group_by"

here is the code:

select religion.Namn
from harförmåga, gudar, religion, hargud
where religion.ID=hargud.ReligionID
and hargud.Gud=gudar.Namn
and gudar.Namn=harförmåga.GudNamn
group by harförmåga.GudNamn
having count(harförmåga.FörmågaID)=
(select MAX(Subquery.Names) from
(select count(harförmåga.FörmågaID) as Names from religion, hargud, gudar, harförmåga
where religion.ID=hargud.ReligionID
and hargud.Gud=gudar.Namn
and gudar.Namn=harförmåga.GudNamn
group by GudNamn )as Subquery);

how do I avoid the error?