In a bowl, mix oregano, mined garlic, lemon juice, olive oil, salt, pepper and sugar.
Set aside half of the mixture to use as dressing. Mix the other half with thawed, peeled shrimp and let it marinate for 10 minutes.
Meanwhile, cut the Persian cucumbers in half lengthwise and then cut each half into pieces. Add it to a large bowl.
Dice the tomato and add it to the cucumbers.
Slice the bell pepper and the onion, add them to the bowl as well. Toss the vegetables until they're combined.
Heat a pan over medium heat and cook the shrimp for about 6 to 8 minutes until it's fully cooked.
Add the cooked shrimp to the salad.
Pour the reserved dressing over the salad and toss well.
Serve immediately.