456820, you played the BIS standar mission v1.7 (at my signature), but it seems you missed half the mission or more
When you talk with the father's girl (the ghost) he commands you to find her daughter, "she is crying alone in the forest" (he also gives you the tip about a healing fountain somewhere). So your primary goal is to find that girl after talking with that ghots. You should look for the girl in the northen forest (the forest where your guarpost is). Once you find the girl, she will give you further instructions, and only after that you will be able to cross the barrier of the southern forest (the forest behind the church's ruins).
That healing fountain works only once, so it is recommended to drink from it only after talking with the girl. If you need healing before that you may use the first aid box inside your tent (at your initial camp N of your guardpost).
BTW, due to a problem with WGL 5.0 BIS objects, the WGL Forest version fountain is the large one (not the small one with the statue above), so the player cannot get close enough to its center drink from it. Of course, drinking from the healing fountain is not mandatory (it is not any objetive), but makes the mission a bit harder as your only can heal with the first aid box in your tent (way North of the southern forest).