- She never told him whether she wished to go or not
Numquam dixit eum utrum voluisset ire necne non
Eum is the wrong case.
Necne by itself is ‘or not’ (only in indirect questions; in direct it is ‘annon’); there is no need to add a ‘non’.
- We hoped to find the very stone with which the general was killed
Speramus repperi lapidem cum quem ducem interficeretur
WHoa there. Verbs of hoping usually take the future participle (to be most elegant, don’t include the esse) and the subject in the accusative case. You forgot to translate ‘the VERY stone’ and your cases for the rest of the nouns are hopeless. There are simpler and more correct ways to express ‘means by which’.
- He asked us where the sword had been put
Rogavit nos ubi gladium passuessit erat
passuessit?? You mean pono in the pluperfect subjunctive. Get rid of erat, you already have a conjugated verb.
- I am trying to learn which hill they will fortify
sum conarens cognoscere quem collem muniantur
sum conarens is English idiom, not Latin. Use the plain present, and remember the verb is deponent. The present subjunctive will not express futurity except in a few unambiguous circumstances. You need a future participle and a form of esse in the subjunctive.