Here are some brief explanations. During the week I swam, fished, and sunbathed a lot. Simple past is used to describe simple facts that already happened. Past Continuous can be used to describe something that happened in the past but was interrupted. During the week, I was swimming, fishing, and sunbathing a lot, whenever the sun was shining. Or I was swimming, fishing and sunbathing a lot during the week, whenever the sun was shining. I enjoyed the time in the Lake District. Use Past Simple to state a simple fact. You can use Past Continuous if there was an interruption. I was enjoying my time in the Lake District when I received a call from work. Use Past Perfect when one thing happens before another. I had enjoyed my time in the Lake District before the summer tourists arrived. Now I miss the friends that I made during my stay there. Simple past describes a simple fact. Hope this helps.

It is better if you write this question under notebooks because that way we get to see the text when we write a comment. I cannot copy-paste the text in my comment using my cellphone.

In the first sentence they are speaking about something that happened in the past "during the week" you went on holiday to the Lake District. Therefore this is part of the weekly routine/habits of this person. We use the PRESENT SIMPLE to speak about present routines/habits.

To speak about past routines/past habits we use:

1. the expression "used to" + verb in infinitive

During the week I used to swim...

2. "would" + verb in infinitive

During the week I would swim...

3. The PAST SIMPLE

During the week I swam...

Complete the sentence using the PAST SIMPLE of the verba in brackets.

The PAST CONTINUOUS is used to show that something continued for some time, continued before and after another action and for sonwrhing that happened before and after a particular time.

Examples:

At eight o'clock last night I was reading a book when my wife got home. My head was aching and my headache was growing.

In sentences 2 and 3 you have to choose between PAST SIMPLE and PAST PERFECT. Which one do you think you have to use in this story and why?

After completing the first sentence, what tense do you think you have to use? Use your intuition to choose the correct answer.

As a native English speaker, I can give you the correct words to use.... but can't answer the follow up questions... As it has been so many years since my formal English classes the terms for language structure escapes me. This makes my Spanish learning more difficult as well. Por qué? Porque. ;). Sorry Not a real answer to your question, just agreeing with you, that the use of a language, and it's formal building blocks are two different worlds.