Japanese Sentence Translation for Karen Aitken

I can handle it : Several ways to translate this, but none of them literal (will only give an equivalent meaning):

1. 頑張る [ganbáru] which is the way Japanese say "I'll do my best (to deal with something)".

2. 大丈夫 [daijò:bu] which is the way Japanese say "it's OK" or "it's going to be OK" or "no problem (I can handle it)".

3. 楽勝 [rakushò:] which is the way Japanese say "piece of cake" or "no trouble at all (in handling it)".

4. 絶対に上手く行く [ze'tài ni umáku ìku] which would mean something like "it's going to work out just fine" or "I promise/I assure you/I bet it's going to be done well/properly skillfully".