17-> if you keep eating fast food, you will not lose weight.

18.-> if you want to make this cake successful, you should whisk the eggs lightly. 

19.-> He must wash vegetables carefully if he wants to eat them raw.

20. -> pumpkin soup has many good sources such as fibre, minerals and vitamins, so we should eat it regularly. 

17.if /you/keep/eat/fast food,/you/not /lose/weight

-> if you keep eating fast food, you will not lose weight.

18.make /this cake / successful,you / should/ whisk/ eggs /light

-> if you want to make this cake successful, you should whisk the eggs lightly. 

19.he/ must/ wash/ vegetables/ careful/ if / want/ eat them raw

-> He must wash vegetables carefully if he wants to eat them raw.

20. pumpkin soup / good source / fibre, minerals and vitamins/ so / should / eat / regular/.

-> pumpkin soup has many good sources such as fibre, minerals and vitamins, so we should eat it regularly.