{{kono you ni} maryoku ga risan shite-shimai} todokanai no desu. このように魔力が離散してしまい届かないのです。 {{Like this} the magic-power ends up dissipating and} [the spell] doesn't reach [the target].
maryoku - mana, MP, literally "magic power." See magic for details.
{{dono you na} shugyou wo sureba} yoi deshou ka. どのような修行をすればよいでしょうか。 [It] would be good {if [I] did {what sort of} training}? How should I train? What should I do to fix this?