These verb forms imply future tense only
karunga - करूंगा (male says -I will do)
karenge - करेंगे (masculine plural subject - 'will do')
jaunga - जाऊंगा (male says -I will go)
ayenge. -आएंगे (masculine plural subject - 'will come')
tha - था is masculine singular verb for 'to be'. it depicts past.
if standalone in a sentence, it means 'was'.
if used in past participle sentences, it can be understood as "had been".