2007 Suzuki Forenza engine and transmission issue

Did you use your flywheel? Are you sure the bolts are fully seated on the torque converter (I am assuming your vehicle has an automatic transmission)

When you installed the torque converter into the front pump, did it properly seat?

Does the engine always stop at the same point? There has to be something causing it to stop. If everything is together properly on the transmission, was the engine running before the repairs?

Is the trans fluid full? Are the cooling lines attached? I assume the converter is turning, and you're sure the converter was properly installed into the front pump?

There is no trans dip stick. Checking the level is not really DIY friendly. It requires jacking the car up (while still being level). A lift is usually used. With the engine running and transmission temperature in the normal range, shift through all gear before checking. Next, remove the upper transmission plug (behind the trans IIRC) with a special 8mm square tool that can be purchased if you don't have one that will work. If oil comes out, it was a overfilled. If no oil comes out, you're supposed to add until it comes out. Be careful because it is really easy to burn yourself on the exhaust.