i'm fairly new to blender (coming from architecture background) so i've used sketchup alot and more advance software for architecture like revit3d/bim.
The work i'm doing now is for jewelery so trying to do this in blender but even the simplest tasks are time consuming.. and frustrating. i'm really doing basic modelling but getting so many problems.
for example i just created a heart shap using half a cylinder (mirrored) and a cube. in edit mode i need the top face to be all one face but for some reason the one edge will dissolve but the pothers won't.. its the same type of edge so i cant work out what to do. The marked yellow edge dissolved but the red won't, its a direct mirror??
if i delete all the faces then select the edges to create a new face for the whole top this also doesnt work as it only creates a faces between randon edges.. again makes no sense.. need help what am i doing so wrong for something so simple.
Image below is all edge deleted except 2d now, still wont face

