Everything from the 2 lessons of this topic on a few pages: the key idea of each lesson, the diagram to remember, the points to learn and the traps examiners set. Read it, cover it, test yourself.
A primary amine has an NH2 group joined to one carbon atom, for example ethylamine (ethanamine), CH3CH2NH2. It is made by heating a halogenoalkane with excess ammonia in ethanol under pressure (in a sealed tube): CH3CH2Br + 2NH3 → CH3CH2NH2 + NH4Br. This is nucleophilic substitution: the lone pair on N attacks the δ+ carbon. The amine product still has a lone pair, so it can attack more halogenoalkane, giving secondary and tertiary amines and finally a quaternary ammonium salt; a large excess of ammonia makes that less likely. The same lone pair accepts a proton, so amines are bases: CH3CH2NH2 + HCl → CH3CH2NH3+Cl−. The electron-donating ethyl group makes ethylamine a slightly stronger base than ammonia.
Use excess ammonia, not excess halogenoalkane, to get the primary amine; excess halogenoalkane pushes the substitution on to secondary and tertiary amines and the quaternary salt. Two moles of NH3 are used per mole of halogenoalkane, because the second one takes the H+. Amines are stronger bases than ammonia, not weaker: the alkyl group pushes electron density onto the nitrogen. The salt with HCl is ionic, CH3CH2NH3+Cl−; nothing is substituted on the carbon chain.
A nitrile contains the –C≡N group, and its carbon counts in the name: CH3CH2CN is propanenitrile. Heating a halogenoalkane under reflux with KCN in ethanol substitutes CN− for the halogen, adding one carbon to the chain. Aldehydes and ketones react with HCN and a trace of KCN by nucleophilic addition to give 2-hydroxynitriles, such as CH3CH(OH)CN from ethanal. Nitriles are hydrolysed by heating under reflux with dilute acid to carboxylic acids, and reduced by H2/Ni or LiAlH4 to primary amines. These steps let you build a longer carbon chain and then turn it into the functional group you need.
A nitrile is named by counting the C of the C≡N group: CH3CH2CN is propanenitrile, not ethanenitrile. KCN must be in ethanol; in water you get an alcohol. HCN adds to C=O by nucleophilic addition, not electrophilic addition as for alkenes. Reducing a nitrile gives an amine with the same number of carbons as the nitrile, CH2NH2 at the end; hydrolysis turns the CN carbon into COOH and releases the nitrogen as NH4+.