Der Patient entwickelte einer Lebensmittelvergiftung?
I'm not a doctor, so this might be how doctors talk about it, however eine Krankheit entwickeln (developing a illness) feels wrong. Also your native speaker completely ignored that it's about the symptoms, not the actual illness (symptoms that fit illness A might actually be caused by illness B!). Entwickeln does fit Symptome if you are talking about an ongoing process (even if it's in the past and at this time already complete). If you want to express that, when examining the patient, certain symptoms were found (that had developed before the examination), you'd go with zeigen instead:
Der Patient entwickelte die Symptome einer Lebensmittelvergiftung.
Der Patient zeigte die Symptome einer Lebensmittelvergiftung.
Das Dach des Tunnels leckte Wasser.
Wasser lecken sound a bit odd, because lecken already included water/liquid (in case of other things it can be specified, for example Gasleck or Ölleck). That said, I don't think lecken is the correct word to use in the first place - lecken means to leak. Seeping however is something a bit different, in most cases better translated as sickern, that has the implication of water/a liquid seeping through natural materials like earth, stone, sand, etc. (while lecken implies the liquid escaping from/through a man-made container/barrier like pipes). A sugested transpation for your sentence would be.
Wasser sickerte durch die Tunneldecke
If you just want to express what you actually can see without implying how the water got there (humidity? broken pipes? aliens?) you could got for a neutral
An der Tunneldecke hatte sich Wasser gebildet
Water had formed on the ceiling of the tunnel
Dieser Straße trägt einen großen Teil von Verkehr.
Sound ok, although it would be vom Verkehr, not von (or if you want to be more gramatically correct you can use the Genitiv des Verkehrs. Den Verkehr tragen ist ok, although you can make it sound a bit better by saying
Die Straße trägt einen großen Teil der Verkehrslast.
Because tragen in this context implies some form of burden/weight (Last), which we can add to Verkehr
Dieser Raum wird 200 oder Mehr Dollar führen.
Sounds wrong. As I understand run in this context means to cost, which would be translated to kosten, not führen. I don't have the context, but if this is about a room you rent at a hotel, room would be better translated as Zimmer, not Raum. Possible translations would be:
Dieses Zimmer wird 200 dollar oder mehr kosten
Das Zimmer wird mindestens 200 dollar kosten
Das Zimmer kostet ab 200 dollar aufwärts
The last phrase ab X aufwärts expresses a base price and implies that it can be more depending on the customers wishes, selection options, additional services, etc.