Je voudrais que quelqu un puisse me corriger ma redaction en anglais parce que j ai certaines difficultes: dire si les phrases ont sens et corriger les erreurs avec les reponses... s il vous plait

Le Voici :
Staying on hold (rester en regrardant) in the front building of the Guggenheim museum, I was watching over two men making a secret deal in the parking lot.
There, the one wearing the brown jacket, he was my client. he had asked me to to follow him for the reason that these last days he had felt someone was shadowing him. And so, he wanted to assure that his important contrat will be well accomplished.
At that moment, through the magnifying glasses, I saw the bag which contained the contrat in question, being delivered to the opponent.
As my work was successful, I was about to leave the scene when I noted something suspicious happening.: An electrician was checking the underground. I quickly took my glasses and looked closer.
Hold on, isn t it a detonator?
Finally got (compris..) the situation, I ran and ran. At last, headed to the decisive spot, I was hastening to get out my client from his car when suddenly the countdown started running: 5,4,3,2,1