I don t know what s wrong with my car?

So when my car wouldn t start I took it in and it turns out it was the starter. The guy fixed it and everything was cool. But when I picked it up it made a weird noise and sounded like it wanted to turn off so I let it run for a little bit and everything was good. The tailpipe had alot of smoke coming out of it also but my uncle told me that was because they had to remove it or something. But anyway I drove home (which was an hour and a half away) and I didn t have any problems, it was running better than it ever has before. But when I got up this morning to drive it it made a weirder noise and I didn t think it was going to start but it did. It just sounded extremely weak and more smoke was coming out of the tailpipe. I made it to school but I m so scared to drive it again. Should I just let it run for a minute before I drive it? Idk some advice would be greatly appreciated. Thanks in advanced.
Added (1). 2002 Ford Focus, idk what engine but people tell me it's a difficult one and that it has 2 motors. White smoke. But last night it eventually stopped. And 1.7k miles. And it's not the head gasket I got that checked already.

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