I hired new contractor on friends reference to cut and install new laminate counter-top on existing base-cabinets.

After he cut the 10' countertop into 3 pieces and installed it on the base cabinets the countertop is not joined together properly and is tilted(is lower at one end).
The counters are also not joined together and have a gap between them of like 1/2".

He is saying that if a countertop is cut it will remain a bit loose between pieces and tilted.
He is saying that for proper installation i should have never told him to cut it into 3 pieces.

He is joining the pieces of countertops using silicon and glue.

Is there any way he can join 3 pieces of countertop together properly?
Is there any way to join the base cabinets together and remove or reduce the gap?