The ş might be confusing to you, but we Turks use ş in a verb to make it what we call işteş (mutual)
So for example
görmek - to see
gör+ş+mek = görüşmek (to see each other, to meet)
selamlamak - to salute or to say hi
selamla+ş+mak= selamlaşmak (to say each other hi, to salute each other)
sevmek = to love
sev+ş+mek = sevişmek (to make love - lit. to love each other)
öpmek = to kiss
öp+ş+mek = öpüşmek (to kiss each other)
with the same way,
anlamak = to understand
anla + ş + mak = to understand each other
anlaştık is pass tense of 1.st plural (i.e we) of anlaşmak
Anlaştık: We understood each other - We made a deal.
Hope it clarifies