Olaf (ice fish) and (enjoy) his time. Later he (catch) a big fish. The fish (get) frozen and Olaf (throw) it back in the lake. Olaf (play) the clarinet. Then Olaf (hit) the tambourine 3 times. Then he (check) how the other instruments (sound). Now Olaf's body parts (play) different musical instruments.

Here is your text with the verbs properly conjugated in the past tense:

Olaf enjoyed his time. Later he caught a big fish. The fish got frozen, and Olaf threw it back in the lake. Olaf played the clarinet. Then Olaf hit the tambourine 3 times. Then he checked how the other instruments sounded. Now Olaf's body parts played different musical instruments.