(Fix) standardize alerts && handle errors from calling contracts methods

[vbaranov]

• (Mandatory) Description
  • standardize alerts at the style of all Dapps
  • handle errors from calling contracts methods like this:

• (Mandatory) What is it: (Fix), (Feature), or (Refactor) in Title, e.g., "(Fix) price of 1 token in Wei > 18 decimals" (Fix)
• (Mandatory) Developers: Each completed PR should be updated in the Wiki Documentation. (Recommended) Each PR should have one commit message and therefore should only contain one specific fix or feature. Otherwise, multiple PRs should be made
• Did you check that your PR is chain agnostic? It shouldn't depend on any hardcoded chainIds, URLs. Yes
• (Optional) Any additional concerns or comments

[vbaranov]

@phahulin @rstormsf is anything stopping you from review?