1 Have to be lenient and be merciful - means not to do things to the extreme, but to leave room for leeway.
2 It is better to do less than to do more - it means not to worry about other things, and the less things to do, the better.
3 When two tigers fight, one of them will be injured - When two ferocious tigers fight, one of them will be injured. It is a metaphor that both opposing sides are very strong, and as a result of a fierce struggle, one side will surely suffer.
4 You cannot have both - you can only have one of the two, not both.
5 Putting a long-term view to catch big fish means taking a long-term view. Although the results may not be immediate, you will get greater benefits in the future.