Sometimes I wonder what was going through Sollozzo's mind when he was trying to make the deal with the Corleones.

There was no subtitles in the scene where Sollozzo and Michael are talking in Italian. I understood Some of it but I couldnt make it out into what they were discussing.

When he met with Michael in Loui's in the Bronx, Sollozzo tells Mike "all i want is a truce" right after he says that Michael says he has to go to the bathroom. Sollozzo then squints his eyes. What do you think Sollozzo was thinking about. Was he jus suspicious?

As Michael correctly figured out, Sollozzo's meeting with Michael was really intended for Sollozzo to buy time for another attempt on Vito's life. Whacking Vito was the key to Sollozzo's plan: as long as Vito was alive, he knew that neither Sonny nor Tom would make a deal with him. Michael was incidental--a place-holder for Sollozzo.
Of course Sollozzo was suspicious of Michael. Even though McCluskey frisked him in the car, Sollozzo still couldn't dismiss the possibility that Michael's trip to the bathroom had ulterior motives.